FM23-81

7/29/2019 FM23-81

1/129

ANK , H6TANKS), 1 9 4 2

^

ntp rrc ~ . f '

7/29/2019 FM23-81

2/129

FM 23-81C3 4 .

BASIC FIELD MANUAL v / ' l * ' '37-MM GUN, TANK, M 6 (MOUNTED IN TANKS)

CH A N G ES ! WAR DEPARTMENT,N o. 3 J W A S H I NG T O N , November 2, 1042.F M . 23-81, April 3 , 1942, is changed as follows:

. FIRING PIN A N D G m > K A S S E M B L Y .(to be disassembled only when absolutely necessary). Press the prongs of

the firing spring stop into the guide and, using the 37-uimcombination tool, drive out the guide pin from the forwardend of the tiring pinguide. With u screw driver * * * firingpiu stop.

Replace the stop * * * firing pin to thefront. Screw the firing pin into the guide as far as it will go,hold the prongs o f the stop into the firingpin, and then backthe firing pin out until the holes o f the pin and guide arealined.' Drive in the guide pin until it is just flush on bothsideso f the guide. Release the pressure on the firing spring stop.Be careful not to injure the guide when removing or replacingthe guide pin.******

[A. G . OC2.11 (10-7-42).] (C 3 , N ov. 2, 1942.) . BR E E C H B L O C K . Actuate the trigger.Remove * * * right hand under it. With the left hand remove the closingspring locking pin. Lower the breechblock andthen remove the lever arm shaft. Remove the crank assemblyand the breechblock together from the breech ring. Disengagethe crank trunnions from the T-slot.

Rotate the upper arms ofthe extractors fully forward. Insert trunnions of crank inthe T-slot upper arm of the crank to the right, and replacecrank assembly and breechblock into the breech ring, keepingthe cocking lever up and pointing to the rear. Support thebreechblock with the right hand. Rotate the crank into position

493083 42

7/29/2019 FM23-81

3/129

FM 23-81BASIC FIEIJ) MANUAL C 3

In line with the holes in the hrtHfh ring lugs. Support thebreechblock in a partially lowered position, and Insert thelever arm shaft into the holes in the breech ring and the crankassembly. Secure the lever * * * allow theblock toclose.

[A . G . 062.1 1 (10-7-42).] (C 3 . N o v . 2 , 1942.). CL O SING S P R IN G A N D HOUSING. (1)Remove the left guard from the gun. itemove thebreechblock. I*evel the gun and remove the coupler key byusing a screw driver and the proper wrench. Slidethebarrelfar enoughto the rear topermit removal of the closingspringhousing. Unscrew the closing spring housing. Compress theclosing, spring * * * retainer, and closing spring.

* * * * * * * 6. Replace the closing spring * * * onto the

housing body. Slide barrel forward and replace coupler key.Replace left guard.

[A . G . 062.11 (10-7-42).] Nov. 2 , 1942.) . FI RI N G A N D E X T R A C T ING M E C H A N IS M G R O U P O F B B E E C HRING (with breechblock removed).

* * * * * * *(3) (not to be removed from gun except when abso

lutely necessary). Remove the left guard from the gun.Level the gun and remove the coupler key by using a screwdriver and the proper wrench. Slide the barrel * * *plunger and spring.*******A. G . 062.11 (10-7-42).] (C 3, Nov. 2, 1942.)6 (Superseded). A D JU S T M E N T O F SIGHTS.

For field and combat firing the telescopic sight M19 isadjusted so that the Hue of sight through the zero range dotand theaxis of the bore are parallel. All spare sights must beadjusted.(1 ) Place tank onfairly level ground .

Place the testing target (fig. 13) at least 80 feet from thegun.

7/29/2019 FM23-81

4/129

FM 23-8137-MM GUN, TANK, M6 (MOUNTED IN TANKS) C 3(c) Place the muzzle sight (fig. 12) In the muzzle that the

bar of the muzzle sight, that is , the straight side of the triangles,Is even with the horizontal marking on the muzzle of the gun.O pen the breech, look through the tube, and manipulate the gununtil the testing target can be seen. Insert the breech sightabout 2 inches into the chamber.Have the testing target moved until It is perpendicular tothe axis of the bore. Sight through the peep hole; manipulatethe gun until the space between the points of the triangles ofthe muzzle is on the center of the gun target of the testing target.Have the testing target rotated in a plane perpendicular to theaxis of the bore, until the bar coincides with th e line Nowrotate the muzzle sight until the edge of the bar coincides withthe vertical marks on the muzzle of the gun. M ove the testingtarget until theedge of the barcoincides with the line

Without disturbing th e gun,manipulate the sight until thezero range dot is at the intersection of the lines andCheck to see that the vertical line of dots coincides with the linethey do not, realine the gun on its part of th e testing

target and readjust the sight.If bore sights are not available, stretch thin strings across

the muzzle using the horizontal and vertical marks on the muzzleto center them. Remove the firing pin guide assembly and usethe hole in the breechblock bushing as a peep sight.

(2) Select a distant aiming pointat least 1,000 yards from the gun. If possible, select an objectsuch as a building, smokestack, or lone tree. With bore sights(fig. 12) or by means of stringsas described above, lay the gunon the aiming point making use of horizontal and vertical edgesto assure accurate aiming. Do not aim on centers of trees orbuildings. Adjust sight on the same aiming point asdescribedabove.

6 . Since this sight has only one horizontal cross hair, this cross hair should be adjusted to give arange setting between 600 and 800 yards. Adjust the sight as inabove, using the intersection of the cross hair as the zero rangepoint. Then lower the line of sight 5 mils by raising th e rearof the sight by means of th e sight adjustment screw. Depending

7/29/2019 FM23-81

5/129

FM 23-81BASIC FIELD MANUAL C 3

on the ammunition being fired, this will give approximately thefollowing range settings : Shot, TP M51 (w/o windshield) (2,450ft./sec. muzzle velocity) 600 yards ; shell, HE M63 (2,800 ft./sec.muzzle velocity) 700 yards; shot APC M51 (2900 ft./sec. muzzlevelocity) 800 yards.

(1) For 1,000-Inchrange firing, the abnormally short range and the miniature target make it necessary to give a nonpurallel relation between theline of sighting and the center line (axis) of the gun. The instructor should explain the reason for this artificial distortionof the line of sighting; he should point out that on a life-sizetarget at a proper range for service ammunition the line ofsighting and center line of the gun should always be parallel;and should also show how the distortion used on the 1,000-inchrange would cause increasingly great errors if the gun wereaimed at more distant targets.

(2) For firing on the 1,000-inch range, both the M19 and theM5A1 telescopic sights areadjusted so that the line through thezero range of the sight and the center of impact coincide at 1,000inches. On a target 1,000 inches distant, fire one round. Centera black paster over the shot hole. Without disturbing the layingof the gun,adjust the sight so the zero range dot or theintersection of the cross hairs, whichever sight is used, is on thecenterof the paster. Fire a confirming round on another paster.

[A. G . 062.11 (10-7-42).] (C 3, Nov. 2 , 1942.)BY OBDEB OF THE SfiCBETABY OF WAS.

G. C . MARSHALL,,O F F I C I A L :J. A. ULIO,

U.S. GOVERNMENT PRINTING OFFICE. 194*

7/29/2019 FM23-81

6/129

FM 23-81

BASIC F IELD MANUAL

37-MM G U N , TANK, M6(MOUNTED IN TANKS)

UNITED STATESGOVERNMENT PRINTING OFFICE

WASHINGTON : 1942

For sale by the Superintendent ofDocuments, Washington, D. C .

7/29/2019 FM23-81

7/129

W A R DEPARTMENT,W ASH INGTON , April 3, 1942.

FM 23-81, 37-mm G un, Tank, M6 (Mounted in Tanks), ispublished for the information and guidance of all concerned.[A . G. 062.11 (1-2-42). |

BY O RDER Of THE SECRETARY OF WAR:G . C. MARSHALL,

O F F I C IA L :J. A . ULIO,

D I S T R I B U T I O N :D2, 7 , 17 (8); R 1 7 (10) ; Bn 9 (2), 17 ( 5 > : C 9 . 1 7(5); 1C 17 (20).(For explanation of symbols see FM 21-6.)

H

7/29/2019 FM23-81

8/129

TABLE OF CONTENTSParagraphs PageC H A P T E R 1 . M E C H A N I C A L TRAINING .S E C T I O N I. Characteristics and description.___ 1-3 1

II. Disassembly and assembly.-------- 4-9 14III. Functioning.---.--------.-------- 10-21 18IV . Care and cleaning of gun, mount,and spare parts.-_____________ 22-31 23V. Stoppages and immediate action. 32-33 33VI. Mounts and sights__._________._ 34-36 35VII. Power traverse^-------___-_-__-_ 37-38 43vm. Accessories and spare parts__ -_ 39-40 43IX. Ammunition-_________________ 41-46 45X. Individual safety precautions^----. 47-51 51C H A P T E R 2. TRAININ G F O R PUTTING G U N IN AC T I O N . 52-54 53C H A P T E R 3. MARKSMANSHIP.S E C T I O N I. General_---______________._-_-_ 55-57 57II. Preparatory marksmanship--____ 58-63 58III. Preliminary gunner's examination, 64 66IV . Range practice, including qualification courses--.--___________ 65-68 67V. Conduct of range practice, including record practice and individualsafety precautions_____-___ 69-86 70C H A P T E R 4 . T E C H N IQUE O F FIRE .S E C T I O N I. General _____________ ________ 86-87 89

II. Characteristics and classesol flre_-_ 88-89 89III. Terrain features and their relationto targets--____________ 90-91 90IV. Types o f targets and ammunitionto be used on each________ 92-93 90V. Range determination__________ 94-96 92VI. Target speeds.-___________ 97-98 93VII. Target designation..------------- 99-104 94VIII. Fire distribution, adjustment, control, and orders___-_-___------ 105-108 97C H A P T E R 5 . C O M B A T F I R I N G PRACTICE.----______ 109-113 105C H A P T E R 6 . A D V I C E T O I N S T R U C T O R S .S E C T I O N I. General-._____________. 114-117 112II. Mechanical training.________ 118-124 113III. Training for placing gun inaction______________ 125-128 114IV. Marksmanship____________ 129-131 114V. Combat firing practice-----____ 132-133 116I N D E X ___________.______-__.-__--________ 118

Hi

7/29/2019 FM23-81

9/129

FM 2& - 81

BASIC FIELD MANUAL37-MM: GUN, TANK, M6 (MOUNTED IN TANKS)

(This manual supersedes so much of section I, Training CircularN o. 39, W ar Department, 1 9 4 1 , as pertains to F M 2 3 - 8 1 . )CHAPTER 1

MECHANICAL TRAININGParagraphs

SECTION I. Characteristics and description_____________ 1-3II . Disassembly and assembly.--,________-__.____ 4 9in. Functioning___________________. 1 0 - 2 1IV . Care and cleaning of gun, mount, and spare parts. 2 2 - 3 1V. Stoppages and immediate action._______ 3 2 - 3 3VI. Mounts and sights.______________.___._ 34 -36Vn. Power traverse,___________________ 37 -38VIII. Accessories and spare parts...__________.. 39 -40IX. Ammunition...__________._.______.___ 41 -46X. Individual safety precautions.__________ 47-51SECTION I

CHARACTERISTICS AND DESCRIPTION . DE SC RIPTION . o. (1 )The 37-mm tank gun M6 is a flat trajectory weaponof the field gun type similar to the M5 gun described inFM 23 - 80 . It fires projectiles which weigh about 2 pounds.T he main features distinguishing the M6 gun from the M5is that it has a longer barrel, the breechblock is operatedautomatically, and the mount is provided with a breechoperating mechanism.(2 ) Although the tubes are mechanicallyinterchangeable, the M5 gun is S V z calibers shorter than theM6 and when assembled in the M6 breech mechanism givesan undesirable breech preponderance. The model numberof each gun is stamped on the to p of the tube about mid-length.

7/29/2019 FM23-81

10/129

BASIC FIELD MANUAL

7/29/2019 FM23-81

11/129

u-1 1 s 2 Cl n>2

FG

2mangM6inmM2rgsdvew

7/29/2019 FM23-81

12/129

BASIC FIELD MANUAL

1 . Left guard. 3. Breech operating mechanism.2 . Breechblock recess.FIGU R E 3.37-mm tank gun M6 in M24 mount, rear view.

The ty pe of mount used with the gun depends upon the type of tank in which the gun is mountedand the position within the tank. When the gun is mountedin the turret of tanks having manually operated turret only,the mount is designed to permit elevating and some traversing independent of the turret. When the gun is mounted inthe turret of tanks having power operated turrets, the mountpermits elevating but all traverse is by the turret.c. The barrel assembly consists of thefo llowing principal parts:

7/29/2019 FM23-81

13/129

37-MM GUN, TANK, M6 1(1) (a) The barrel is a one-piece forging withrifled bore threaded to screw into the breech ring. Thereare two bearings, one near the breech end and one at m id-length that support the barrel and aline it in the yokes of

the sleigh. The front bearing has a flange at the rear andis threaded for a lock nut to secure the position. K ey waysin the right and left rim of the flange engage keys in th eyoke to prevent rotation of the barrel.(b) The lower part of breech ring is recessed on eachside of the bore to form extractor pockets. The lower partof each pocket has been drilled to hold the extractor springsand plungers.(2) (a) The breech ring is bored andthreaded in front to receive the barrel and is secured to thebarrel by a locking key. Holes bored in the lugs on the bottom of the breech ring provide means for attaching thebreech ring to the recoil mechanism and the lever arm shaft.The rear hole is for the lever arm shaft.(b) The rear half of the breech ring is slotted vertically

to receive the breechblock. The rear of the breech ringis U-shaped to facilitate loading (see fig. 3). The cylindricalstuds inside the ring serve as extractor pivots. The holethrough the lower left wall forms the trigger bearing anda counterbore inside provides a pocket for thetripper.(c) A breech operating mechanism containing the operating cam and guide is bolted to a pad located on the rightside of the recoil cylinder (see fig. 3).(d) The closing spring housing is attached to the lef tforward end of the breech ring.(3) The extractors are positioned against theside w alls of the breech recess. The lips of the longer upperarms lie in pockets on each side of the chamber and engagethe flange of the cartridge. Camming lugs on the lowerarms project inward to engage the cammed surface of the

breechblock. (See fig . 4.) The camming lugs being heldtothefront by the extractor plunger springs lock thebreechblock in the open position by engaging the locking studs onthe face of the breechblock. Two holes in the rear face ofthe breech ring contain the extractor springs and plungers.(4) (figs. 4 and 5). The

7/29/2019 FM23-81

14/129

1 BASIC FIELD MANUAL

breechblock assem bly consists of the breechblo ck, bushing,and firingspring retainer pin. The large center hole in thebreechblock houses th e firing pin guide assembly . Thebreechblock bushing is screwed into the forward end of thehole and machined off. The firing spring retainer pin andthe interrupted shoulder inside the hole form a joint to holdthe firing spring retainer and pi-event rotation. Grooves inthe hole receiv e and guide the cocking and sear lugs of thefiring pin guide.

1 . Cocking lever.2 . Firing guide retainer.3 . T-slots.4 . Sear pin.5 . Locking lug.6 . Beveled face.

F I G U R E 4.- -Breechblock.

7/29/2019 FM23-81

15/129

00< \ J< \ J

1 . Bn-eehblock.2 . T-sIot.8 . Cocking lever,4 . Cocking leverplunger spring. " > . C o rk i n s r leverplunger.6. Sear.~ . Sear spring.x . .Sea r retaininglock.0. Sear pin.10 . Oukle.

11. (Juide pin.12. Stop.13. Retracting spring.14 . Firingpin.15. Firingspring,1 ( 5 . Retainer.17. Crank.18. Operating lug.10. T-bandle.20. Trunnion.21. Extractor, left.22. Extractor springs.

23. Extractor piu n -gers.24. Extractor, right,25. Breech operatingmechanism.Breech operatingcam.27. Lever armshaft.28 . Trigger.29. Trigger spring.30 . Trigger plunger.31. Tripper.FIGURE 5.Breechblock assembly; firing pin and guide assembly,crank, extractors, and breech operating mechanism.

7/29/2019 FM23-81

16/129

0

5 2o H e r-

FG

6awshwnfnanoanmnsm

7/29/2019 FM23-81

17/129

37-MM GUN, TANK, M61 . Closing spring.2 . Closing spring housing.Closing spring nut.4 . Closing spring rod.5 . Link pin.6 . Lever arm shaft link.7 . Closing spring lock pin.8 . Lever arm shaft.9 . Trigger.10 . Operating lug.11 . Operating cam.12 . Crank trunnion.Upper arm of tripper.14 . Sear.1 5 . Sear lug.

16 . Breechblock bushing.17. Firing pin.18 . Firing spring.19 . Firing pin retractingspring.20. Firing spring retainer.21. Breechblock.22. Cocking lever.23. Cocking lever plungerspring.24. Cocking lever plunger.25. Breech ring.26. Stop.27 . Guide.28. Coupler key and nuts.

(b) The bottom of the breechblock is cut from front to rear by a T-slot which inclines downward to the rear. Thecrank trunnions slide in the T-slot to raise and lower thebreechblock. The to p of th e block is U-shaped to guide theshell into the chamber and has a beveled surface to forceth e shell home as the block rises, A hole with a slot for thesear arm is on the left side of the block; it houses and guidesthe sear and sear spring. The upper left side of the blockis recessed to receive the cocking lever. A hole in th e rearface of this recess houses the cocking lever plunger andspring. Portions of the right and left sides of the breechblock have been cut away to reduce weight. Locking studsare provided on the breechblock face to hold th e breechblockin the open position. Two stopping lugs on the rear baseof th e breechblock stop its upper m ovement.(5)(a) The firing spring bears rearward on the retainer andforward on the stop.2 . The sear is notched for engagement of the sear lugof the guide. The sear passes through the breechblock horizontally, perpendicular to the guide andthe sear and spring aresecured by a pin.The cocking lever pin pivots in a hole in th e upperleft side of the breechblock. The upper arm projects upward and rearward from the block andterminates above the rear wall of the breech ring.The lower arm extends forward and downward,terminating ina lug which engages and forces the

7/29/2019 FM23-81

18/129


fir ing pin guide rearward to cock the mechanism.A plunger and spring return the lever to positionas the u pper end is re leased .The tripper, trigger, trigger plunger, and spring aresupported in the breech ring.

The tripperis within the breechring. The operatingarm of the tripper extends upward and carries acam su rface fo r actuating the sear. The lowerarm of the tripper carries a horizontal safety lu g,which in the idle positionof the trigger and tripper,extends inward below and forward of the left loweredge of the breechblock. Lowering theblock placesthis shoulder behind the lug of the tripper andprevents actuation when the breech is open. Thetrigger is mounted on the tripper hub.

2 . The trigger consists of a tapered arm with a hollowcylindrical hub; the hub enters a hole inthe breechring. The trigger plunge r and spring whic h areseated in the cheek of the breech ring retain thetrigger in position and return it to a forward position after firing.(1)The recoil cylinder houses the recoil mechanism and is assembled with the trunnion pins which are mounted in thetrunnions of the yoke.

< 2 ) The recoil cylinder is provided withrails whic h guide the sleigh during the movement of thegun. The gu n and the piston ro d of the recoil mechanismare connected by a coupler and coupler pin. A shouldergu ard is also bolted to the recoil cylinder.

(3 ) The sleigh is of built-up steel constructionand mounts the gun barrel in yokes.(4) The trunnions are made in two halves,

doweled to each sid e of the recoil cylinder and lo cked bya screw.(5 ) The recoil system is the hydrospringtype. It includes the recoil mechanism, which absorbs therecoiling energy of the gun after it is fired; the counterrecoilmechanism, which returns the gun into battery; and the

10

7/29/2019 FM23-81

19/129

S

T

L

HOOK,

69 S

S o

7/29/2019 FM23-81

20/129


buffer mechanism which absorbs the last portion of thecounterrecoil action to prevent damage to the weapon dueto sudden stopping of th e movement of the recoil parts.(1) Adjustment of the gun inelevation is transmitted from the handwheel to the barrelby a shaft and a system of gears (see flg. 1).

(2) For quick aojustment of th e gun in elevation, theworm gear drive is equipped with a throw-out lever whichdisengages the gear drive and permits free movement ofthe gun. This release mechanism is actuated by pullingout (to the right) th e throw-out release handle springactuated lock and pushing the throw-out handle forward toits farthermost position. To reengage the gears and lockthe gun to the elevating mechanism pull out ( to the right)the throw-out release handle spring actuated lock and pullthe throw-out handle to the rear. It locks in the rearmostrecess w h en the worm gear segment and sector gear arepositively engaged.

/. (1) In tanks equipped w ithpower traverse mechanism the gun is fixed in the mount andtraverse is obtained by rotating th e turret. This is accomplished as described in paragraph 38 . The power traverseturret may also be manually operated.

(2) In tanks equipped with manually operated turrets only,the gun can be traversed 10 right and left from the centerby means of a knob and swivel shaft to the traversing bar.The traversing knob lock when tightened locks the gun fortraverse. When the gun is not locked for traverse the friction of th e gears is such that either free movement of thegun may be obtained for traverse or adjustment may bemade by means of the traversing knob. When traverse ofthe gun beyond the traverse permitted by the mount is necessary, th e turret must be rotated or the tank turned indirection.

(1 ) In tanks equipped with powertraverse mechanism the gun is firedelectrically by a solenoidfiring device connected with the tr igger. The solenoid firingdevice is actuatedby a switch on th e pow er traversing lever.A forefinger safety lever on the control grip must also bedepressed to fire the gun. The gun may be fired by manual12

7/29/2019 FM23-81

21/129

3 7-MM G U N , TANK, M6 1-3operation of the trigger actuator mechanism. (See ( 2 ) ( Z > )below.)

(2) In tanks not equipped with a power traverse mechanism two means of firing the gun are provided in the formof tw o types of trigger actuators:(a) The first consists of a trigger actuator assembled intothe hub of the elevating w heel and consists of a plungerbutton, spring cable, actuator plunger, andwith or withouta trigger lever.(b) The second consists of a trigger bar pivotedat approximately the center in a bracket affixed to the base of the recoil

cylinder, the left end of which engages directly with theactuator plunger. It consists of a bar, pivot pin , and retracting spring.The shield varies in design and thickness withthe mount used. It is attached to the yoke and recoil cy linders by bolts or, in some tanks, direct to the turret.

The traveling lock is hinged by meansof bo lts to a bracket mounted inside the turret. In thetraveling position it is fastened to a bracket on the recoilcylinder. In order to prevent undue wear on the elevating mechanism, whenever the gun is not being operated,the elevating worm gearshould be disengaged fromthe gear sectorand the traveling lock engaged. When the gun is tobe usedthe lock should be in the raised position in theturret top.The spent case deflectoris bolted to the recoil cylinder and has suspended from ita bag to receive the spent cases. . G E N E R A L D A T A .

Total weightof gun (approx.)______ 700 pounds.Length of barrel_____,_________ 78inches.Traverse (manually operated turret) _ _ 1 0 LtolOR.Elevation________________ 10 to +20.Length of recoil-____________ 6 to 8 inches.Capacity recoil cylinder,,______ 5pints.

. A M M U N I T I O N A N D SIGHTS. See paragraph 3 5 and sectio n IX .

44757042 2 13

7/29/2019 FM23-81

22/129

4-5 BAS I C FIELD M A N U A L

S E C T I O N IIDISASSEMBLY A N D ASSEMBLY

. G E N E R A L . The disassembling and assembling described herein can, unless otherwise noted, be done with thegun mounted in the tank. Any disassembly or assembly notdescribed in the follow in g paragraphs is a function of ordnance personnel only.

6. A ll members of the tank crew must be taught to disassemble and assemble the various groups of the gun asdescribed in the following paragraphs.5. F IR IN G PIN A N D G U I D E A S S E M B L Y . The firing pin and guide assembly may beremoved from the breechblock with the block either in orout of the gun. Close the breechblockand actuate the triggeror if the breechblock has been removed from the gun, placeit with the firing pin guide retainer toward the operatorand retainer slot in vertical position. With the right handpress the retainer into the breechblock about inch androtate it either w ay one-quarter of a turn (rotate slot tothe horizontal position). Release the pressure and removethe retainer and the firing spring. Cup the left hand overthe recess in the rear of the breechblock and with the righthand rotate the cocking lever forward smartly. The firingpin guide assembly will be ejected.

(to be disassembled only when absolutely necessary).Using the 37-mmcombination to ol, drive out the guide pin from the forwardend of the firing pin guide. With a screw driver unscrewthe firing pin from the guide and remove the firing pin,retracting spring, and firing spring stop.Replace the stop into the guide with theprongs protruding through the forward end of the guide.Place the retracting spring onto the firing pin and insertthe firing pin and retracting spring into the guide with thestriker end of the firing pin to the front. Screw the firingpin into the guide as far as it will go and then back it off

14

7/29/2019 FM23-81

23/129

Justenough to clear the hole for the guide pin. Drive in theguide pin until it is just flush on both sides of the guide.Be careful not to injure the guide when removing or replacingthe guide pin.Insert the firing pin guide assembly intothe firing pin guide chamber in the breechblock. Make surethe sear lug on the bottom of the guide is down (the searlug is cut off at an angle) and the stop is to the front.Hold the trigger to the rear (push the trigger bar forward)and push the firing pin guide assembly forward until theprongs of the stop strike the breechblock bushing. R eleasethe trigger. Insert the firingspring into the guide. Placethe cupped endof the retainer over the rear end of the firingspring, keeping the slot on the rear face of the retainerhorizontal. Press the retainer into the face of the breechblock about inch and rotate it until the slo t is in thevertical position; then release the pressure.

. B R E E C H B L O C K . a . Actuate thetrigger. Remove firing pin and guide assembly (par. 5o).Pull dow n on the crank until the hole in the closing springrod coincides with the hole in the housing body . Insert aretaining pin in these holes to hold the closing spring rod.Support the breechblock by placing the right hand underit. W ith the left hand remove the closing spring lockingpin and then the lever arm shaft. Withdraw the crank andremove the breechblock.(1 ) Insertthe index fingerof the left hand between theapron of the cocking lever andthe nose of the cocking lever plunger. Depress the plungerand at the same time remove the cocking lever with theright hand. Be careful not to let the plu nger or spring fly outof the breechblock. Release the plunger and remove it andthe spring.

(2) Place the breechblock with thefront face down. Press the arm of the sear in to its recessas far as it will go and remove the sear retaining lock andwasher. Release the pressure and withdraw the sear andsearspring.

c. (1 ) Place the searspring over the small end of the sear and insert the sear

7/29/2019 FM23-81

24/129

6-7 BASIC FIELD MANUAL

and sear spring into the sear recess in the breechblock. Alinethe aim of the sear with the slot and press the sear intoits recess as far as it will go. Replace the sear retaininglock and washer. Release the pressure on the sear spring.(2 ) Insert the cocking lever plunger springinto its hole in the top of the recess in the left side of thebreechblock. Press the cocking lever plunger into the hole,flat end against the spring. With th e index finger of theleft hand depress the cocking lever plunger and, at the sametime, with the r ight hand replace the cocking lever in itsrecess, short arm of the lever down. Release the pressure.

Rotate the upper armsof th e extractors fully forward. Start the breechblock intoits recess in the bottom of the breech ring keeping the cockinglever up and pointing to the rear. Support the breechblockwith the right hand. Insert the crank trunnions in theT-slots in the bottom of the breechblock, upper arm of thecrank to the right. Rotate the crank into position in linewith the holes in th e breech ring lugs. Insert the leverarm shaft into the holes in the breech ring and the crank.Secure the lever arm to the link by inserting the closingspring rod. Release th e T-handle and allow the breech toclose. To test the operation of the breechblock pull downon the T-handle until the breechblock is opened and locked.Press forward on the tips of the extractors with the baseof a shell case to unlock the breechblock and allow the blockto close. C L O S I N G S P R I N G A N D HOUSING.a . (1)Remove the breechblock. Unscrew the closingspring housing. Compress the closing spring slightly to enable another operator to remove the retaining pin. Gradually release the pressure. Remove the closing spring assembly. Unscrew the housing body screw and remove the housing body and the housing body pin. Rem ove the lever armshaft link pin, the link, the retainer, and closing spring.(2) To remove the closing spring without removing its housing, remove the breechblock and reinsertthe crank, lever arm shaft, and closing spring lock pin. Pushdown on the operating lug until the hole in the closing springrod is in line with the hole in the housing. Insert a retain-

1 6

7/29/2019 FM23-81

25/129

37-MM G U N , T A N K , M6 7-8ing pin through both these holes. Release the operating lugand remove the closing spring lock pin. Remove the retainingpin and push the closing spring assembly out the front of thehousing.

N O T E. T he closing spring and housing will be removed and disassembled only In case of necessity.Replace the closing spring and closing springretainer on the closing spring rod. Attach the lever arm shaftlink by means of the link pin. Attach the housing body toth e breech ring by means of the dovetail connection and thehousing body pin. Screw in the housing body screw. Insertthe closing spring assembly into th e housing body with thelever arm shaft link first. Compress the closing spring sufficiently to enable another operator to insert a retaining pinthrough the centered holes of the housing body and the closing spring rod. Connect the lever arm shaft and link bymeans of the closing spring lock pin. Remove the retainingpin and screw the housing onto th e housing body.

8 . FIRING A N D E X T R A C T I N G M E C H A N I S M G R O U P O F B R E E C H RING(with breechblock removed). (1)Rotate the extractors to a vertical position and removethem from their pivots. The extractor spring plungers andextractor springs are removed by ordnance personnel only.(2) Reach into the breech recess from below,grasp the tripper with the fingers and withdraw it from thetrigger hub.(3 ) (not to be removed from gun except whenabsolutely necessary).When necessary to clear th e triggerfrom the recoil guard, level the g un and remove the couplerpin by using a screw driver and the proper wrench. Slide thebarrel back to between the apron and the trigger plunger andpress the plunger rearward to free the lug on the triggerapron. H old the plunger depressed and remove th e t r iggerto th e left. Release the pressure on the plunger and remove

the plunger and spring.(1) Replace the trigger spring andplunger and press the trigger plunger to the rear, slide thetrigger hub into the hole at the top of th e notch until theshoulder contacts the cheek of the breech ring. Release the17

7/29/2019 FM23-81

26/129

9-10 BA SIC FIKLD M A N U A L

plunger. Slide the barrel to the forward position and replacethe coupler pin.(2 ) Insert the shaft of the tripper into the hub

of the trigger with the short arm vertical. Slide the trippershaft through until the flattened end o f the shaft enters thesJo t in the trigger hub and the short armof the tripper entersits recess inside the breech ring.(3 ) K eeping the lips of the extractor up andto the front, engage the shoulders of the extractor in the extractor plunger. While forcing the plunger in against theaction of the extractor spring, slide the extractor onto thepivot.

9 . To D I S A S S E M B L E T R I G G E R A C T U A T O R A S S E M B L Y . (1) D isconnect the cable of the 37-mm trigger actuating mechanismfrom its housing (left side of gun mount), by loosening theA lien setscrew in the trigger actuating housing using theH e-inch Alien setscrew wrench. Remove the end of the cablefrom the housing.(2 ) R emovethe tw o cap screws (using '/^-inch bo x wrench)holding the trigger actuating housing to the body o f theshoulder rest. Remove the recoil cylinder cross head bolt(using 1 J ?l6-inch wrench on nut). Pull the gun tu be to therear about 6 inches and remove the trigger actuating housingto the right (under the gun tube).

N O TE. Normally the trigger actuator assembly will be disassembledonly to the extent required to attach the trigger cable . O n tanksequipped with solenoid firing devices, extra devices will becarried and tank crew s will be permitted to replace theseonly .Proceed in reverse order of disassembling.

S E C T IO N HIFUNCTIONING

1 0 . enlisted man should have a working knowledge of themechanical operation of the gun so thathe will be able to keep it in actionduring combat. A lthough18

7/29/2019 FM23-81

27/129

37-MM CON, TANK , M6 10-13many parts of the gun operate simultaneously, the subject offunctioning is divided into phases to facilitate instruction.The explanation of mechanical functioning begins with theassumption that the gun is unloadedand breechblock open,

b. The breech mechanism of the gun is designed to beeither operated by hand or automaticallyopened by theforceof recoil. 1 1 . PIHST PHASE L O A D ING. A s a round is inserted into thegun chamber the cartridge rimstrikes the lips of the extractors and rotates them forward into the pockets in thebreech face of the tube. A t the same time, the low er armsof the extractors are disengaged from the breechblock andthe block moves up to the closed position under action ofthe closing spring. With the breech closed, the lower armof the cocking lever projects forward clear of the cockinglug on the guide. 1 2 . S E C O N D PHASEA CTION O F T R I G G E R A C T U A T O R . a . OnA pushon the button in the center of the traversing handwheelm oves the cable, through its flexible housing, so as to forcethe actuator plunger to the rear. The actuator plu ngercontacts the lower portion of the trigger arm and movesthe trigger to the rear. Upon release of the disk plunger,the actuator plunger spring forces the actuator plunger toreturn to its forward position.

b. When the safetytrigger on the pistol grip control of the power traversing system is pressed, the toggle firing switch (thumb buttonsw itch on some tanks) may be closed. When the switch isclosed the solenoid firing device, through linkage causes thetrigger arm to rotate tothe rear. 1 3 . THIRD P H A S E T R I G G E R A C TI O N . A s the lower arm ofthe trigger is forced to the rear, the trigger hub operatingon the tripper shaft, moves the upper arm of the tripperforward. As the tripper arm moves forward it forces thesear to the right until the sear notch is in line with thesear lug on the firing pin guide and the sear lug can thenmove forward through the sear notch.

19

7/29/2019 FM23-81

28/129

14-15 BAS IC FIELD MANUAL1 4 . F O U R T H P H A S B O P E R A T I O N or F IR IN G PIN O O T D I A SS E M B L Y . spring being compressed betw een th ebase of the stop and the retainer, forces the firing pinguide assembly forward. The prongs o f the stop strike the breechblock bushing and stopthe actiono f the firing sp ring .The firing p in and guide, since they are locked together bythe guide pin, continue forward under inertia to strike th eprimer and fire thepiece. During this movement the retracting spring Is being compressed between thebase of the stopand the heado f the firing pin. The striker end o f the firingpin strikes the prim er and stops the forw ard movement o fthe guide Just before it contacts the breechblock bushing.The retracting spring which has been compre ssed then retracts the guide and firing pin to their norm al position withthe firing pin point flush with, or sligh tly in rear of, thefront face of the breechblo ck. 1 5 . F I FTH P H A S E B A C K W A R D M O V E M E N T O F B A R R E L A S S E M BLY. The action of the pow der gases on the breechblock atthe moment o f discharge causes the recoi l of the barre lassembly and drives it rearward about 8 inches. The reco ilis resisted , its speed regulated, and the movement stoppedby the action o f the reco il mechanism which is attached to the barrel assembly by the coupler and couple r pin. As thepiston head in the re coil cylinder moves to the rear withthe piston rod , tw o fo rces resist the movement, the tw ocounterrecoil springs are compressed and the movement ofthe piston head is resisted by the o il in the cylinder. Theoil follows tw o courses as it f low s to thefront of the pistonhead:a. It forces the pis ton valve back against the resistance ofthe pis ton valve spring and f low s through the holes in thepiston head are uncovered as the valve moves awayfrom the piston.

It passes through the ports, thence through the ho llow port ion of the forw ard end of thepiston rod and out aroundthe tapered buffer. As the barrel assembly moves backw ardthe piston rod movesaway fromthe tapered buffer (w hich isgradually opened) thus the oil is restricted greatly at theinstant of discharge and restricted le ss and le ss as the barrelassemblymoves to the maximumlength of recoi l. The com -

20

7/29/2019 FM23-81

29/129

37-MM GUN, TANK, MB ' 15-18binatlon of the resistance of the counterrecoil springs andthe restriction of the oil stops the rearward movement ofthe barrel assembly at the maximum recoil without appreciable shock to the gun.

c. A s the barrel assembly moves to the rear, the lower armof the trigger is forced to the front by action of the triggerspring and plunger. This motion of the trigger causes theupper arm of the tripper to move to the rear,withdrawingthe safety lu g on the lower arm of the tripper from underthe lower surface of the breechblock, thus permitting thebreechblock to open. A bevel surface on the lower left guideof the breechblock also forces the tripper forward should thetrigger spring be broken. 6 . SIXTH P H A S E A U T O M A T I C OPENIN G O F B R E E C H . D u ringrecoil the lu g on theright-hand side of the crank is cammedin the crank cam of the breech operating mechanism. Thismovement causes the trunnions of the crank to slide downward in the T-slot to open the breech. A s the crank rotates,the lever arm which is keyed to the crank rotates to therear and brings with it the link and the closing spring rodand compresses the closing spring. The downward m ovement of the breechblock is stopped by the impact of the stopsurface of the crank hub on the shoulders of the breechblock ring.17 . S E V E N T H PH A S E A CTION O F E X T R A C T O R S . A s thebreechblock nears its lowermost position, the cam shoulderson thefront face of the breechblock contact theround camson the lower ends of the tw o extractors. This imparts asharprearwardthrow to the extractor lips on the upper armof the extractor. Since the extractor lips are behind therim of the shell, the case is extracted from thechamber andejected clear of the breech end of the gun. The breechis thenopen ready for loading. The camming lugs on the bottomof theextractorsare held tothe front by the extractor springplungers and lock the breechblock in the open position byengaging the locking studs on the face of the breechblock. 18 . E IGH TH P H A S E C O CKING A C T I O N . A s the cocking leveris carried down with the breechblock, the projecting armof the cocking lever is forced forward by the cam surface

21

7/29/2019 FM23-81

30/129


inside the rear wall of th e breech recess. The lower armIs rotated rearward to engage the cocking lug on the firingpin guide and to move the guide toward the rear. Thisrearward movement of th e firing pin guide assembly compresses the firing spring sufficiently to permit the engagement of the sear. (As th e guide is moved to the rear, thesear lug cams the sear to the right. When the sear Jugclears the sear, the sear springs to the left and in frontof th e sear lug under the action of the sear spring andholds the firing pin guide assembly to the rear in the cockedposition.) 19. NINTH P H A S E F O R W A R D M O V E M E N T O F R E C O I L I N GPARTS. a. Recoil being stopped, the recoiling parts are instantly moved forward by the action of the compressedcounterrecoil springs against the piston bracket. The pistonvalve, by the action of the valve spring, closes the holesin the piston head as the counterrecoil starts. The oil hasonly one course to follow through the hollow end of thepiston rod and the ports in its walls to the rear of thepiston head.b. The added restriction during the counterrecoil causesthe barrel assembly to move slowly back into the battery.

c. The final movement is stopped by the action of thecounterrecoil buffer entering the hollow end of the pistonrod. The counterrecoil buffer, due to its tapered construction, progressively closes the hollow portion of the pistonrod through which the oil must flow. This action throttlesth e flow of oil and permits the g un to return to batterywithout appreciable shock. 0. RECOCKING.The firing mechanism can be cockedwithout opening the breech, by rotating the projecting armof the cocking lever forward and releasing it. 21. S A F E T Y F E A T U R E S O F FIRING MECHANISM.a.(1) As the breechblock is lowered, the left shoulder of theblock passes immediately to the rear of the safety lug onthe lower arm of the tripper, thus preventing the operation of the tripper and holding the trigger in the forwardposition until the breech is closed.

22

7/29/2019 FM23-81

31/129

3 7-MM GUN, TANK, H0 21-22(2) W hen the breechblock starts to open the bevel on th efront of the lower left guide forces the tripper forwardif it has not already been forced forward by the actionof thetrigger spring and trigger.b. offset lower arm of the cockinglever engages the cocking lug of the guide early in thedownward movement of the breechblock and remains inthe path of this lug until the block is returned to approxim ately its closed position. This eliminates the possibilityof having thefiring pin move forward to strike the cartridgedue to the premature release of the sear or other failureon the part of sear to hold the mechanism cocked untilthe breech is fully closed.

the breechblock is loweredit carries the firing pin down with it, thus the firing pinwill not be alined with the primer of the shell except whenthe breech is fully closed.S E C T I O N IV

CARE AND CLEANING OF GUN, MOUNT, A N D SPAREPARTS 2 . G E N E R A L C A R E . a . Laxity in proper care and maintenance will soon result in deterioration to the extent of appreciably reducing the accuracy and dependability of the gun.It must always be kept clean and covered with a light coatof oil. Car e and cleaning is not confined to the gun alonebut includes the mount, spare parts, and all accessories.Ammunition must be kept clean and dry. Guns mountedin vehicles should be locked in the traveling position unlesstheir early use is anticipated. Muzzle covers are providedto prevent dirt from entering the gun through the bore.Detailed information pertaining to cleaning, preserving, andlubrication materials and their authorized use will be foundin TM 9-850. The use of materials other than those authorized for the purpose mentioned is strictly forbidden. Dirtand grit which accumulate on the gun and mount and inthe operating mechanism while traveling, and from the blastof the piece in firing, settle on the bearing surfaces. T his

23

7/29/2019 FM23-81

32/129


dirt and grit in combination with the lubricant form a grinding compound. Powder fouling attracts moisture and hastensthe formation of rust. Therefore, whenever possible, as during lulls in combat, dean the g un as soon as practicable afterfiring. Dirt on nonbearing surfaces can usually be removedby water. Lubricated or other greasy parts must be cleanedwith a dry-cleaning solvent applied with a rag. The procedure in cleaning the bore, chamber, and breech ring is coveredin paragraph 2 4. The following materials are issued by theOrdnance Department for use in the field (see SN L K-l):(1) This is used fo rcleaning the bore, breech mechanism, and firing mechanismafter firing.(2) is used for removing greaseIt is preferred to kerosene because it does not leave a corrosivefilm. The use of gasoline is prohibited because it is tooinflammable.(3 ) is the coarsest abrasive permittedfor cleaning mist and stain from bearing surfaces.(4) This is used in cleaning unfinished ornonbearing surfaces only. It is issued in 5 of coarseness, ofwhich "00" is the finest.(5) This is issued for cleaning the bore.(6 ) These are fo rgeneral cleaning purposes.Tank commanders are responsible for the daily inspection of the 37-mm guns and immediately take the proper

action necessary to keep the g un in excellent condition. 3. S P E C I A L PRECAUTIONS.The following precautions shouldbe taken in the use and operation of the gun:o. Remove the firing pin guide assembly before removingthe breechblock.Do not put a strain on the recoil guard or shoulder restwhile getting into or out of the vehicle.c. Do not put unnecessary strain on the actuator or solenoidcables.Lock the gun in the traveling position unless early useis contemplated.

24

7/29/2019 FM23-81

33/129

37-MM G U N , TANK, M6 23-24e . D o not attempt to open the breechblock while actuatingthe trigger./. D o not flre the gun before the recoil tube has been

checked for the proper amount of recoil oil.D o not jam thegears at maximum and minimum elevating points.D o not disconnectthe worm gear sector without supporting thebreech end of the gun.i. If the firing device fails to flre make certain the gun isnot set on safety. Jiggle it slightly.D o not load the gun until use is contemplated.f c . D o not leave a live round in the chamber of a hot gun.Inspect to see that gun is unloaded before placing it inthe traveling position.The precautions for coaxially mounted machine gun areas given in FM 23-50. 4 . C A R E A N D C L E A N I NG. The exterior partsshould be protectedwith a film of oil after every drill. Thegun will be thoroughly cleaned and protectedat least once aweek andimmediately following itsuse in inclement weather.For garrison cleaning the procedure indicated for care andcleaning after firing in below, should be followed exceptthat the bore and chamber will not be swabbed with wateror soda ash solution but w ill be cleaned with a dry ragand then oiled. If, upon inspection, no corrosion is detected,a coating of rust-preventive compound (cosmic) m ay beplaced in the bore andchamber insteadof light oil.5. Before drill or firing, the gun isinspected forproper functioning, lubrication, and cleanliness.W hen firing is contemplated the recoil cylinder is checkedfor proper amount of oil (see par. 26). A ll mechanism, particularly trigger actuator, and other exposed surfaces arecleaned and oiled as necessary, and are manually tested toinsure proper functioning.c. The bore and chamber should be swabbedfrequently. The breech, firing and trigger actuator mechanism, and other exposed surfaces are cleaned and oiled asnecessary.

25

7/29/2019 FM23-81

34/129


d . soon as practicable alterfiring, the bore, chamber, breech ring, breechblock, firingm echanism, and trigger actuator shouldbe cleaned and oiled.The recoil cylinder should be filled and the guides of thesleigh and rails of the recoil cylinder cleaned and oiled ifnecessary.

(2 ) After removing thebreechblock and firing mechanism in the breech ring , thoroughly sluice and sponge the bore and chamber with a solution of pound of soda ash in 1 gallon of water, or hotwater and issue soap , hot water alone, or in the absence ofthese with cold water. Then swab the bore and chamberwith dry waste or rags until they are perfectlydry. Inspectthe bore and chamber for any remaining residue. If theyare not clean, repeat the sw abbing and drying . A smallpiece of burlap jute used as a patch over the end of thebrush of therammer is effective for cleaning the bore. W henall powder fouling hasbeen removed, dry theboreand chamber thoroughlyand cover witha lightcoat of lubricatingoil.Whenever the soda ash solution is used for cleaning, all ofthe parts cleaned should be swabbed or rinsed with clearw ater and dried before oiling. It is of particular importance,when using a cleaning process like the one described above,that all parts and surfaces, recesses, etc., be thoroughlydriedbefore they are oiled. The parts of the firing mechanismremoved from the breech ring and the interior of the breechring should be cleaned with a dry ragand then wiped withan oily rag. Apply one or two drops of oil to the closingspring.

(3) Having removed the breechblock fromthe breech ring, disassem ble it. With a dry rag clean thedirt and oil from the block and all parts contained therein.Lubricate all recesses for moving parts with light oil. Withan oily rag wipe the breechblock and all other parts of thefiring mechanism leaving a thin coating of oil.(4 ) The solenoid and pistonshould be cleaned. A ll exposed and accessible parts of thetrigger actuator mechanism extending arm should be thor-

26

7/29/2019 FM23-81

35/129

37-MM GUM , TANK, M6 24-25oughly cleaned and oiled. Dry-cleaning solvent w ill assistmaterially. This mechanism is particularly vulnerable tomud and dust accumulated while traveling or during actionand unless given careful and detailed care will fail to operatefreely .(5) Clean the outer surfaces, usingdamp rag or dry-cleaning solvent when necessary, then dryand wipe all exposed metal parts with an oily rag. D o notapply oil to painted surfaces. O il collects dirt and grit andmakes daily cleaning more difficult.5 . L UB RICATION.a. Excessive wear can be prevented bykeeping the materiel clean and well lubricated. The life ofthe materiel depends on proper lubrication. Particular attention should be given to sliding and bearing surfaces ofthe cradle and breech mechanism.

Lubricating oils and greases as shown in the lubricationchart must be used as prescribed. N o lubricantsother thanthose prescribed will be used without the authority of theOrdnance Department. (See lubrication chart on followingpages.)c . Lubricating fittings w ill be painted red for ease inlocating. Oilholes areencircled by a red ring.

The oil gun should beworked slowly and the parts oiledshould be maneuvered to insure proper distribution of thelubricant.Should an oiler valve stick and prevent the passage of

the oil, it may be lo osened with a piece of wire pushedthrough the hole. Care should be taken not to damage thevalve./. Care must be taken when cleaning oil and grease compartments to insure the complete removal of all residue orsediment. Dirt or other foreign matter should not be allowedto drop intoany of the lubricating compartments.

27

7/29/2019 FM23-81

36/129

26 BASIC FIELD MANUALLUBRICATION CHART,

Partslu bricate*! (name)

Traversing mechanism:Traversing gears (open)Traversing rack - - -Elevated mechanism:Elevatinggears (open) ...........Elevating rack....... ............Trigge r actuator. ...Elevating gears (M24) (inclosed)

Cradle:

Oun:Bore ........Firing mechanism, cable bushing.Firing mechanism, breechblockand ring.Miscellaneous:Pintle pins (topand bottom).. .Exposed friction points and bearing surfaces.

No.

1

1

1

2

Frequency

Miles

,. _ . . - _

.... .

Time

Daily ....-.do ......do..........do.......Monthly

Daily...

DailyMonthlyDaily ...

Daily...

Method ofapplication

Oiler ...........do..................do..................do......... ..Hand... ....

Oiler... .............do. .......Oil cup . . .

(See remarks)Grease fittingsOiler.. ...

Oil cups... ........Oiler. .. ...........

*In general where lubrication is required and not mentioned in this chart, th e1 . Pack bearings with grease, O. D., No. 0 .2 . and lubricate with the above described oils.3 . Clean and lubricate with th e above described oils.4 . Clean and fi ll with the above described oils.

2 6 . FILLING R E C O I L CYL INDER . The re coil cylinder mustbe kept filled in accordance with the fo llowing instructionsor damage to the gun will probably result. The OrdnanceDepartment will furnish thepropergrade of oil for the recoilcylinderoil, recoil, heavy, low pour-point. The substitution of any filler other than that issued by the OrdnanceDepartment is prohibited .

28

7/29/2019 FM23-81

37/129

37-MM GUN, TANK, M6 26tank gun,

Required lubricantsBelow32 F. Above32 F.

Amount

SAE 1 0 i SAE 3 0 Light film

do i do.Grease O . D., No. 0

SAE 1 0.do

. .-doLightcoating..

j[Light film ....SAE 30 i-.--do..do Light film

Grease, O. D., No. 0. ._ [ Several turns onSAE 10..

SAE 1 0 .

SAE 3 0 . grease gun.Light filmFill

SAE 30. Light film

Remarks

Clean and lubricate daily.

Do.Coat onassembly.

>Avoid waste.For care and cleaning, follow prescribed instructions inpar. 2 4 .Test frequently. Clean an d lubri

cate.

/Avoid waste. Make sure no heavy1 gre ase is on the firing pin guide.

fc llowing procedure will apply:

b . The amountof oil in the recoil cylinder should be suchiat the movement of the gunin recoil is smoothand of uni-tormly decreasingvelocity, and the maximum point of recoil|s reached without shock; thecounterrecoilmechanism wil licn return the gun completely to battery without shock.P o o rapid recoil, and shock at the end of recoil is usuallysaused by too little oil in the recoil cylinder. Failure to

447570 2 9

7/29/2019 FM23-81

38/129

26 BASIC FIELD M A N U A Lreturn completely to battery is usually caused by to o muchoil in the recoil cylinder or may be due to lack of lubricationor th e presence of foreign matter on the guides or rails.c . To fill the recoil cylinder proceed as follows:

< 1 > Elevate the muzzle slightly.(2 ) Pill the oil gun with oil. When filling, keep the nozzlewell under the surface of the oil supply to avoid drawing inair. After filling, point the nozzle upward, push the pistonuntil the oil starts to flow in order to force out any air inthe oil gun.( 3 > Remove the front ( filler* plug and screw the nozzleof th e oil gun into position in its stead, keeping a slightpressure on the oil gun piston as the oil gun is being seated(4 ) Remove the rear plug in the right side of the recoilcylinder.(5) Introduce the o il into the recoil cylinder by slowlypushing on the piston of the oil gun until the oil flow s outof th e rear hole.(6 ) Fully depress th e muzzle (approximately 10) andcontinue to slowly force oil through the cylinder and outof th e rear hole until no more bubbles em erge with the oil(7 ) Screw in the rear plug tightly.(8) Fully elevate th e muzzle, unscrew the oil gun, andreplace the front plug.The filling of the recoil mechanism should be carefullydone to insure that all air has been "bled off" and that th emechanism is completely full. T he presence of air can bedetected by "air bubbles" appearing in the oil. After completing the above filling process, it is sometimes found necessary to drain off a small amount of oil from the recoilcylinder. T his e stablishes a "void" which compensates for anexpansion of the o il during firing. If draining is foundnecessary , elevate th e muzzle slightly and unscrew (crack)the rear filler plug sufficiently to permit about one table-spoonful of oil to flow out. The amount of oil in the mechanism should be such that the gun returns completely intobattery and does not end the action of recoil with anyappreciable jar.Excess oil used during filling should be caught in a cleanreceptacle and must be strained through a clean cloth beforebeing used again.

30

7/29/2019 FM23-81

39/129

3 7 -MM G U N , T A N K , M 6 27-2827. P R O T E C T I O N A N D C L E A N I N G O F M A T E R I A L A F F E C T E D B YGAS .o . (1) For material which ts in constant dangerof gas attacks, whether from gas clouds or gas shells, care

should be taken to keep all bright parts of the gun, mountings,and accessories w ell coated w ith oil.! (2) A ll bright parts of guns and mounts, together with all[accessories and spare parts exposed to the gas, must be[cleaned and wiped dry as soon as possible after the attack,and in any case within 24 hours, after which they should bethoroughly coated afresh with oil. T he same applies to contaminated ammunition. Ammunition which for any reason?hasnot been oiled must be cleaned and oiled.(3) Sights and all instruments should also be covered with|oil and protected with covers when not in actual use, caret>eing taken that the oil does not come in contact with anyIglass or find its w ay into the interior of the instruments.(4) A ll uncapped fuzes or fuzes which have been removedjfrom their containers should be w iped over with oil as soonas possible and protected with a cover.b.lit must be remembered that practically all fabrics and{material such as wool, cotton, rubber, and oilclo th can be(penetrated by mustard gas if exposed to it a sufficient lengthof time. Mustard gas is absorbedby these materialsand pen-jetrates them by a slow process of diffusion. In general, itmay be said that the greater the length of time allowed for?penetration, the greater the danger in wearing these articles.:Por instance, rubber boots which have been worn in an areashelled heavily with mustard gas may be a grave danger tomen w ho wear them several days after the bombardment.Fabrics thoroughly impregnated with boiled linseed oil willresist penetration by mustard gas over an hour,but after thistime these articles are dangerous because the mustard gasdissolves in the linseed oil and they must be destroyed. 8 . DIS INFECT ION O F M A T E R I A L A F F E C T E D B Y M U S T A R D A N DO T H E R V E S I C A N T G ASES. The following measures should betaken for the removal of gas from various materials andequipm ent (weapons, projectiles, cases, wood, metals, rope,etc.) which have come in contact w ith mustard gas. For all

3 1

7/29/2019 FM23-81

40/129

28-31 BASIC FIELD MANUALof the operations indicated below, the gas mask and protective clo thing, including protectiveshoes and gloves, must beworn.a. Commence by freeing the objects of dirt, excess grease,and liquid with wooden spatulas and rags.t > . Swab the gun, mountings, and accessories with rags saturated in kerosene. If kerosene is not available, gasolinemay be used but extreme care must be exercised to avoidpossibility of it becoming ignited.c . Spray the parts with a solution of noncorrosive decontaminating agent, using the IV^-Quart or 3-gallon decontaminating apparatus. After 15 minutes, w ash this off withsoap and water, w ip e dry, and applya thin layer of oil. Bury,or preferably burn, all rags and wooden spatulas used in theprocess, atthe same time insuring that no personnel are inthe immediate vicinity downw ind.Alternatemethods employ a solution of bleaching powder,hot sodium sulflde, or "green solution" in place of the non-corrosive decontaminating agent. For further informationon decontamination,see FM 21-40. 9 . C A R E D U R I N G C O L D W E AT H E R . I n cold weather, the gunmechanism should be tested frequently by hand manipulationto in sure that it is functioning properly. 0 . C A R E A N D C L E A N I N G F O R S T O R A G E . I f the w eapon is tobe stored or if climatic conditions areconducive to the formation of rust, thoroughly clean all parts and inspect for thepresence of corrosion. If no corrosion is present, cover a llexposed metalsurfaces thoroughly with a coating of rust-preventive compound. 1 . POIN TS To BE O B S E R V E D B E F O R E , D U R I N G , A N D A F T E RFIRIN G . (1) See that bore is clear and cleanand remove excess oil.(2 ) See that working parts of the gun are clean, oiled,and functioning smoothly .

(3 ) See that the telescopic sight is clamped firm ly andheadrest adjusted.(4 ) Secure sufficient supply of ammunition.(5 ) Check position of body and make sure no one is in thepath of recoiling: parts.(6 ) Load when directed.32

7/29/2019 FM23-81

41/129

37-MM GUN, TANK, M6 31-33b. (1) Observe the functioning of the gunto anticipate failures and lubricate working parts whennecessary.(2 ) Check bore and chamber for obstructions.(3 ) Continually check the functioning of the recoil.(1) Clear gun.< 2 ) Disassemble the breech. Clean and oil the parts carefully to prevent rust.< 3 ) Swab the bore, with hot water and soda ash whenpossible, immediately after firing, then dry thoroughly andprotect with a light coating of oil.< 4 ) Up o n assembling, check the operation, insuring thatthe gun is functioning properly.(5) Release the firing spring by pressing the trigger.(6 ) Dismount the telescopic sight (where applicable), cleanthoroughly.(7) At first opportunity inspect all parts and make neededrepairs.(8 ) Replenish ammunition when directed.

SECTION VSTOPPAGES AND IMMEDIATE ACTION

3 2 . GENERAL. A stoppage is cessation of fire caused bythe malfunction of the g un or ammunition.b. Immediate action is the procedure used to promptly reduce a stoppage.c. M ost stoppages are prevented by proper care and cleaning of g un and ammunition. 3 3 . S T O P P A G E S , THEIR C A U S E S , A N D I M M E D I A T E ACTION.a.(1 ) (a) Gun on safety or safetyswitch not pressed.(b) Gun fails to return completely to battery.(c) Breechblock fails to close.(d) Defective trigger actuator mechanism, or defective sole

noid or switch.Broken or bent trigger arm.(/) Broken, bent, or burred firing pin.( f i r ) Weak or broken firing spring,(ft) Dirty or defective sear.

33

7/29/2019 FM23-81

42/129

33 BASIC FIELD MANUAL< i > W eak or broken sear spring.< j > Dirty sear lu g or firingpin guide.tfc) Dirty firing pin and guide assembly.(? ) Lack of lubrication.< m > Defective ammunition.(2 ) Check to see if the gun is onsafety. If it is, take it off safety, relay, and fire.< b > Gun is not on safety. Check tosee if the gun has returned to battery. If it hasnot, push itinto battery by hand,re lay , and flre. If the gun cannot be pushed into battery,unload, check recoilcylinders for proper amountof oil. Drainout about a teaspoonful if necessary. If gun sti ll will not re

tu rn to battery, check slides and guides for burs, dirt, andlack of lubrication. Clean, remove burs, lubricate, reload ,re lay, and flre. II the burs cannot be removed turn the gunover to the ordnancefor repair. (Thegun may be continuedin action by pushing it intobattery each time. It should bechecked and repaired at the first opportunity.)< c > Check to see if breechblock hasclosed . If breechblock has notclosedClose it manually, relay, and flre.If it will not close, see if ammunition is seated. Ifammunition will not seat, remove round, reload,relay, and fire. If ammunition still will not seat,clean chamber, reload, relay, and flre.3 . Ammunition is seated. Check for broken or wornextractor,replaceas necessary. Check for brokenor w eak closing spring. Adjust or replace as necessary. Clean and lubricate bearing surfaces ofbreechblock as necessary,(d ) Breechblock is closed. Recock thepiece.If cocking action shows that thepiece is still cocked(indicatedby noresistance other than the cockinglever spring to be overcome) examine for bent orbroken tr igger arm andfor malfunction of triggeractuator mechanism. Replace parts as necessary,relay, and flre. If trigger mechanismis not defective, remove firing mechanismand check forweakor broken firing spring.

34

7/29/2019 FM23-81

43/129

37-MM G U N , TANK, M6 33-342 . If cocking action indicates that the firing pin guidesear lu g has been released from the sear (indicatedby heavy resistance to cocking action), relay andfire. If gun still fails to flre after twice repeating

this action, remove firing pin andguide, clean, lubricate, replace defective parts , re-cock, relay, and flre.If gun still fails to flre, wait 2 unload, loadwith a new round, relay, and flre.If cocking action show s that the firing pin guidesear lug will not remain engaged in the sear, after2 unload, disassemble breechblock, cleanand replace defective parts.b . (1) (a) Defective or dirtyA m m u n i tio n.(b) Dirty chamber.' (c) Bound loaded with insufficient force to trip extractor.(2) S ee a

7/29/2019 FM23-81

44/129

34-35 B A S I C F I E L D M A N U A Lgun is mounted and dismounted by ordnance personnel only.The modified M 22 mount will be used in the light tank. 5. S I G H T S A N D How MOUNTED .Two types of sights arefurnished for the 3 7 - m m tank gun M 6: the telescopic sightM 5A1; and the periscopic sight M 19 with the periscope M 2.a. 8). (1 ) The telescope M 5A 1 is the present standard for use with the M 22mount. The telescope is a straight tube type, using a lenserecting system . The objective end is designed to providea very small frontal target, which also requires only a smallhole in the armor plate (shield). The telescope has a magnifying power of 1 to 1 . 1 2 diameters and a field of 31.Vertical and horizontal lines (cross hairs) are etched in thereticle of the sight.(2 ) The telescopic sight is mounted on tw o brackets. The front bracket has a push f it bearing to accommodatethe forw ard end of the telescope. The rear bracket housesone of several types of adjustment devices used to target thegun.

(3 ) (a) The type of sightadjustment device on the rear bracket will alter slightly theprocedure for installing the sight. A t present the adjustm ent of the sight is accomplished by one of three methods:Pour screws located radially about therear bracket.2 . A n eccentric ring housed in the rear bracket.Vertical and horizontal slides housed in the rear

bracket and operated by means of thumbscrews.(The Wildrick sight adjusting bracket.)(b) The procedure for mounting the sight in the morerecent m odel is described below. For detailed informationon the other types see the pertinentTechnical Manual.Rem ove sight from case.2 . Remove headrest.3 . Loosen wing nut and open swing bolt on clamping

bracket.Insert sight, tapered end forward, through frontbracket and push forward until front bearingis seated in front bracket.

36

7/29/2019 FM23-81

45/129

37-MM GUN, TANK , M6 355. Seat anticant pin in itsseat in lowerhalf of clamping bracket.C lose clamping bracketand swing bolt andtightenwing nut.

Adjustment is made by turning elevation deflectio nthumbscrews in the desired direction. O ne clickequals mil.Replace and adjust headrest. Particular attentionmust be given to this adjustment. It should beadjusted for the gunner while his head is heldin the firing position. In the firing position thehead should be pressed forwardagainst the headrest. The headrest is so adjusted that while thetank in motiontheey es do not press against theprotective rubber over the eyepiece of the telescope causing vision to be blacked out.

F IG URE 8.Telescopicsight M5A1 .

FIGURE 9 . M S A 1 telescopic sight reticle.(1 ) This sight is designed for use withguns mounted in power operated turrets.The sight assembly consists of the periscope M 2 and telescope M 19mounted in a case (fig. 10).

37

7/29/2019 FM23-81

46/129


F IG U R E 10,Periscopicsight with periscope M 2 and telescopic sightM 19(2) The periscope has two mirrors, one top and one bottom , mounted in the case. The telescope is mounted vertically within the case on the right-hand side. The sight

assem bly is mounted in the tankby slipping the case handledown into the sight recess (see fig . 10), clamping it intoplace, andplacing the batterycontainer in the clips providedabove the sight.(3) (a) The telescope M 2 is a straight tube telescope withno magnification. Some of these sights have been issuedwith the cross hair reticle similar to the telescopic sightM 5A1 . (See fig . 9 .) The reticle to be used on latest sig htsis as shown in figure 1 1 . The vertical axis is marked bythe vertical lines above the upper and lower dots respect ively . The figure is self-explanatory as to the meaningof the various dots. The reticle is illuminated by a smallbulb .

38

7/29/2019 FM23-81

47/129

37-MM G U N , TANK, M6 35-36

YOF IGURE 11.Reticle telescopic sight M 1 9 .

i f t ) On some mounts, the sight is mounted in prolongationof th e axis of the trunnions of the mount. Adjustmentsof th e telescope are made by the adjusting screws. (Seefig. 10.) On other mounts the sight is connected to themount trunnions by linkage and adjustment is made bothby adjusting the linkage and by means of the adjustingscrews on the sight. 36. How T O Z E R O SIG H TS. For field range and combatfiring, the sight is adjusted so that the line of sight andth e axis of the bore are parallel. For 1,000-inch rangefiring, the sight is adjusted so that the line of sight andthe center of impact of the 37-mm g un or the machine gun,whichever is being used, intersect at 1,000 inches. Threemethods are used to zero the sights.a. The bore sights issued with the 37-mmg un consist of a muzzle sight and a breech sight. (Seefig. 12.) A testing target (see fig. 13 ) issued by the O rdnance Department or improvised m ay be used with th e boresights.(1) T he testing target is placedin a plane perpendicular to the axis of the bore at a distanceof 80 feet from the gun. The tank should be on fairly levelground. Place the sight about inches into the

39

7/29/2019 FM23-81

48/129

36 BASIC FIELD MANUALmuzzle of the gunwith thebore of the sight in line with thehorizontal marks in the muzzle of the gun. Insert thebreech bore sight about 2 inches into the chamber of thegun. Look through th e bore sights and have the testingtarget moved until the center line of the bore pierces thetesting target so as to bring thehorizontal line of the muzzlebore sight coincident with the horizontal line on theright handfigure of th e target. Now, rotate the muzzle bore

(5) MUZZLESIGHT.

TRIANGLES.

7/29/2019 FM23-81

49/129

37-MM GUN , TANK, M6 36( 2 ) Place bore sights in the bore.Select a distinct point on which to aim at a range of at least600 yards. Aim on this point with the bore sights . Without

M22 mount.

M24 mount.FIOTJM ! 13.Testing targets.

disturbing the laying of the gun, adjust the sight so as toaimon theselected point.b . -Remove the firing pin andguide assembly from the gun. Select an aiming point atleast 2 ,000 yards from th e gun. By looking through thehole in the breechblock bushing, bore sight the gun on the

41

7/29/2019 FM23-81

50/129


42

7/29/2019 FM23-81

51/129

3 7 MM G U N , TANK, M6target. Without disturbing the laying of the gun, adjustthe sights on the target.c. Fire a shot on any pointof the target with the machine gun. Center a black pasterover the shot hole. Without disturbing the laying of thegun, adjust cross hairs (600-yard dot) of the sight on thetarget.

SECTION VIIPOWER TRAVERSE

3 7. POWER TRAVERSE. W hen guns are mounted in tankshaving power operated turrets, all traverse in by the turret.For description of the power traverse see appropriate Technical Manuals. The power traverse turret may be operatedmanually by engaging the manual operating handle.3 8 . O PERATION . The power traverse mechanism is controlled by an operating handle on which is mounted the safety ,trigger and firing switches for the 37-mm gun and the coaxi-ally mounted machine gun. This handle has a pistol grip.Rotation of the grip clockwise causes the turret to move tothe right and rotation counterclockwise causes movement tothe left. The speed of movement of the turret is controlledby the amount of such rotation. The gunner grips the control with his left hand, with his fingers grasping the safetyswitch and his thumb in position to operate the firingswitches.

SECTION VIIIACCESSORIES AND SPARE PARTS

3 9 . ACCE SSO RIES. Accessories include tools for such assembling and disassembling as are covered in section II, makingadjustments, and cleaning gun, as well as auxiliary equipment. The names or characteristics of the accessories provided with the gun indicate their use, therefore, no detaileddescription or method of use is outlined herein. A completelist of accessories may be found in SN L A-45 . The principalaccessories used the gun crew consist of(1 ) The bore brush is madeof fiber bristles. The lower end of the brush is provided

7/29/2019 FM23-81

52/129

MANUAL

with an external threaded stud which can be screwed into thethread end of the forward section of the rammer. The brushis carried in th e tool kit.(2 ) The rammer consists of tw o sections. The forwardsection is threaded at both ends. O ne end is threaded toreceive the cleaning brush and the other end the rear sectionof the rammer. The muzzle cover (M3 02 ) isprovided to protect the gun from dirt, moisture, or obstructions. It fits over the muzzle of the gun. It is made of heavyleather and protects the bore from dirt and water.can is for recoil cylinder oil. Itis carried in its compartment of the tool case.This is the spout type oiler. Itshould be filled with light lubricating oil and carried in thetool case. This grease g un fits thelubricating fixtures of the g un and mount and is carried inthe tool case./. This oil gun is used in refilling therecoil cylinder. It is made of brass and has a fixed threadedspout which fits th e filler hole of the recoil cylinder.f i r . This roll is made of canvas and is desig nedto carry the tools. The tools furnished with the guns are:(1) Hammer, machine, ball-peen, 8-ounce.

(2) Pliers, combination, slip-joint.(3 ) Punch, drive pin, standard %2-inch point, 4 inches long.(4) Screw driver, regular, 3-inch.(5) Wrench, adjustable, 8-inch.(6) Wrench, engineer's, double head, %-inch and J/2-inch(7) Wrench, socket, head, setscrew, %2-inch hexagonal.(8) Wrench, socket, head, setscrew, %-inch hexagonal.(9) The tool roll and tools are carried in the crew compart

ment of the tank. 40 . S P A R E PARTS. The spare parts fo r the g un and mountsare listed in th e Standard Nomenclature List.

44

7/29/2019 FM23-81

53/129

3 7-MM GUN , T A N K , 41S E C T I O N IX

AMMUNITION 41 . A M M U N I TIO N U S E D . a . Ammunition authorized for useto the37-mm tank gun,M 6, islisted in thetable belo w . N ote fhat the table completelyidentifies the ammunition as to typeand model of theprojectile and thecaliber and model of thegun in which fired.

Nomenclature

Canister, fixed , M 2, 37-mm guns M 3, M 5, and M6.--_Shell, fixed, HE, M 63, with fuze, BD, M 5 8 , 37-mmguns M3, M 5, and M 6.Shell, fixed, HE, Mk. II, with fuze, BD, M38A1, 3 7 -mm guns M 3, M5, andM6.

Shot, fixed, AP, with tracer, 37-mm guns M 3, M5,and M 6.

Shot, fixed, TP, M SI, with tracer, 37-mm guns M3 ,M S, and M 6.

Cartridge, blank, 10-gage, 37-m m guns M 3, M 6, andM 6 3 .

Cartridge, drill, M13, 37-mm guns M 3, M 5, and M6 i

Prescribed fuzes

M odel

M 58 1 .M 38 A11.

Action

. : :

j Approximateweight ofprojectile(pounds)1.8 91.611.241.9 2

1.92

1.92

1 This fuze is notclassified asbore safe. NDNondelay.

: 3 Requires adapter, shot shell (10-gage), M 2 . This adapte r consists o f a standardCartridge case modifie d by the addition of a liner which is chambered fo r a standardW - g age shotgun shell.

44757042- 45

7/29/2019 FM23-81

54/129

41 BASIC FIELD M A N U AL

oIDU.

If .s

a

cV .

46

7/29/2019 FM23-81

55/129

7/29/2019 FM23-81

56/129

2

PROX

RAF S

D12

88

FG

URE1 9

She

shot g

un10-

ga ge

blank

8gr a

insbl a

ckpo

wde r

with

dr yf

w ads)

5 o

UMB E

R

M ANU

ACU RE R

B E RO

GUNA N

DM O

D EO f

~E

CAE

7GM 3 a

5R1

C AR

R DGE

MCT

P GU R

E20

Cart idg

e dr i l

M 13

Y P

E OF SH E

CAUB E

R AN D

M ODE

O FG U

N

R AF SD

w f 0 2 a

7/29/2019 FM23-81

57/129

5. Drill and blank ammunition are provided for specialpurposes when no targets are to be fired at or for simulatingfire. Blank ammunition may also be used for firing salutes. 2 . L O T N U M B E R.a. When ammunition is manufactured, anammunition lot number, which becomes an essential part ofthe marking, is assigned in accordance with pertinent specifications. This lot number is stamped or marked on eachloaded complete round, on all packing containers, and onthe accompanying ammunition data card. It is required forall purposes of recordincluding reports on conditions, functioning, and accidents in which the ammunition i s involved.To provide for the most uniform functioning, all of theroundsin any one lot of fixedammunition consistof(1) Projectile of one lot number, such as J 321 5 30 - P 6 3.(2) Fuzes of one lot number (when the projectile is fuzed).(3) Primers of one lo t number.(4) Propellent powder of one lot number.To obtain the greatest accuracy in any firing, successiverounds should be from the same ammunition lot wheneverpracticable. 3. D A T A C A R D . A 5- by 8-inch card, known as ammunitiondata card, is packed in eachpacking box with the ammunition. When required, assembling or firing instructions areprinted on the reverse side of the card. 4 . PA C K I N G . T w e n ty rounds are packed in sealed metal-lined packing box. The following data for the armor-piercingammunition are considered representative for estimatingweight and volume requirements:

Complete rounds without packing material-___ 3.420 rounds in metal-lined packing box____.__ 1 0 0 2.3The over-all dimensions of the packing box are ITV s by12iy 6 by 172% 2 inches. 5. PAINTIN G A N D MARK ING. (1 ) A ll projectilesare painted to prevent rust, and by means of the color to

4 9

7/29/2019 FM23-81

58/129

provide a ready means for identification as to type. Thecolor scheme is as follow s:Armor piercing-_ - - - - -Black. 'For 37-mm projectiles whichcontain no explosive fil leror only a tracer.)High explosive-__ _ _ ._^Yellow.Practice _..___-___-_-_Blue. (Projectile may be inert orm ay contain a live fuzewith spotting charge ofblack powder.)Inert (dum m y or drill)--Black. (Contains no explosive.)

(2) In the case of packing boxes, a blue band paintedthereon indicates that the box contains practiceammunition.(1) The following information is stenciled onthe projectile:m) Caliberand type of cannon in which fired.(b) Kindof filler.(c) Mark or model of projectile.Lotnumber of loaded projectile.(2) Because the lot number of the loaded projectile is ordinarily not required after assembly of the complete round,it is stenciled below the rotating band where it is coveredby the neck of the cartridge case.(3) The follow ing is stenciled on the base of the cartridgecase: Ammunition lot number.(& ) M odel of projectile. 6. C A R E , HANDLING. A N D P R E S E R V A T I O N . a. Completerounds and ammunition components are packed to withstand conditions ordinarily encountered in the field. Theammunitiondescribed hereinis packed in sealed, metal-linedpacking" boxes. Nevertheless, since explosives are adverselyaffected by moisture and high temperature, due consideration should be given to protect it.& . Explosive ammunition must be handled w ith appropriate care at all times. The explosive elements in primersand fuzes are particularlysensitive to undue shock andhightemperatures.c. Do not break moisture-resistant seal until ammunition

is to be used.50

7/29/2019 FM23-81

59/129

37-MM GUN, TANK, M6 46-49

Do not attempt to disassemble any complete roundsor any fuze.Do not allow ammunition to be exposed to the directrays of the sun for any length of time. M ore uniform firingis obtained if therounds are at the same temperature./. The complete round should be free of any foreign matter (sand, mud, grease, etc.) before loading it into the gun.If it gets w et or dirtywipe itoff at once.Rounds prepared for firing, but not fired, w ill be returned to their original packings andappropriately marked.Such components will be used in subsequent fir ing in orderthat stocks in opened packings may be kept at a minimum.Do not handle duds. After firing, fuzes are extremelydangerous. Duds are disposed of in accordance with TM 9-1900.

S E C T I O N XINDIVIDUAL SAFETY PRECAUTIONS

47. GENERA L . This section prescribes the safety precautions to be taken by individuals duringpractice in firing the37-mm tank gun M 6 in order to minimize the possibility ofaccidents. (See A R 750-10 and TM 9-1900.)48. P R E C A U T I O N S D U R I N G P R A C T I C E F IRING. a. A ny individual who observes a condition which makes firing dangerouswill immediately call C E A S E F I R I N G and if at a distance fromthe unit firing, will make the prescribed signal therefor.Firing will cease immediately at the command C E A S EF IR IN G regardless of the sourceof thecommand.c. No firingwillbe done exceptunder the direct supervisionof an officer.Guns will be loaded only on command of the officeror noncommissioned officer in chargeof the firing.Firing w il l commence on any range only after it hasbeen determined that the range is clear and the officerin charge of firing gives the order: CO MMENCE FIRING.49. INSPECTION D U R IN G F IRING . Before each day'spractice firing, each gun wil l be inspected to insure that thebore is free of obstructions and that excess oil or greasehas been removed therefrom.

5 1

7/29/2019 FM23-81

60/129

b. After firing and prior to moving thegun from a firingposition, itwill be inspected by an officer to see that it isunloaded.c. The gun will be cleared as prescribed in paragraph 54before anyone moves in front of the muzzle or the gun ismoved.5 0. P R E C A U T I O N S B E F O R E FIRING.a. The gunner will checkhis position to make certain he is not leaning against theshoulder guard and that no part of his body will be in thepath of the gun upon recoil.The loader will check his position to be certain his bodyis clear of the rear of the gun. (See ch. 2.)c. Ammunition will be inspected to see that it is clean andfree of grease and oil.The individual safety precautions listed in paragraph 54will be taken during the firing of the gun.5 1. MISFIRES. When a misfireoccurs proceed as in sectionV .b. When rounds which misfire are removed from the gun,theywill be placed at a designated point away from the gunposition. They will be destroyed under the direct supervisionof an officer in accordance with specific local regulations orin accordance with instructions contained in T M 9-1900.

7/29/2019 FM23-81

61/129

CHAPTER 2TRAININGFORPUTTING GUN IN A CTIO N

2. G E N E R A L . a . The drill of the tank crew is covered inPM 17-5.6 . Training for putting the gun in action is held for thepurpose of developing precision and speed of movement in order that the gun may be effectively operated. The tankcommander, gunner, and assistant gunner (loader) mustfunction as a well-coordinated team in order to obtain themaximum effectiveness of thegun.c. Equipment is loaded into the tank under the supervis ion of the tank commander. The gunner installs the sight.When action is not imminent, the gun is locked in thetraveling position. W hen actio n is im m inent, the gun is releasedfrom its firing position.action in abandoning a disabledtank and for mounting and dismounting from the tank see PM 17-5 .

53. P O S I T I O N S O F G U N CREW . (1) The gunner sits on the seat to the left ofthe gun, places his right hand on the elevating handw heel,his left hand on the power traverse operating handle, andhis head against the sight headrest. He makes sure thatno part of his body i s in the path of the recoil of the gun.(2) The assistant gunner stands on the right side of thegun or sits in the seat on that side. H e m akes su re that nopart of his body is in the path of the recoil of the gun.

f t . XI)The gunner either stands on the left of the piece or occupiesthe gunner's seat.(2) (a) The left hand is placedon the actuating knob of the elevating handwheel, theshoulder firm ly against the shoulder guard and the rightarm under the gun mount w ith the right hand on the right-handsupport bracketwhereby he actuates eithergun, 37-mm or caliber .30 , with his right thumb. (Because of the recoilof the gun, he avoids extending his right arm over the

53

7/29/2019 FM23-81

62/129

BASIC FIELD M A N U A Lshoulder guard.) He operates the elevating mechanismwith his le ft hand and the traversing mechanism byphysical pressure against the mount. The position is mostapplicable when firing the gun, in combat, from positionsof partial tank defilade.t b) The gun may be traversed by means of the traversinghandwheel. In this method of firing the turret gun(s),the right hand is placed on the traversing handwheel withthe thumb on th e caliber .3 0 trigger actuator. The 37 - mmgun must then be fired, using the left hand, by means ofthe trigger actuator plunger in the hub of the elevatinghandwheel.

(3) (a) The left hand graspsthe mount by means of the hand support bracket on theleft. The shoulder is firmly against the shoulder guard andthe right arm under the gun mount with the right handon the hand support bracket on the right of the mount.The guns are actuated with the right thumb. The gunneris trained to elevate, traverse, and fire the gun simultaneously in an accurate and rapid manner.(b) The assistant gunner takes post, as in a(2) above,on the right of the gun in such position that will avoidhis injury by the recoil. 4 . S E R V I C E O F T H E PIECE.(1) The gunner, assisted by the assistant gunner, checksthe recoil cylinder for proper amount of oil. He then

(a) Installs th e sight and checks the light in th e M19sight wh e n that sight is used.(ft) Checks thegun for cleanliness and lubrication.(c) Checks the trigger actuator mechanism.Checks traversing and elevating mechanism.Takes h is position at the gun.(2 ) The assistant gunner assists the gunner in checkingthe recoil cylinder. He then(a) Inspects th e ammunition for proper amount, types,loading, and cleanliness.(Z Inspects to see that no rounds or empty cases areon the floor.(c ) Checks

Date post:	14-Apr-2018
Category:	Documents
Upload:	jdnwotc
View:	215 times
Download:	0 times