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STEN Mk II Build

Printed From: Weaponeer.netForum Name: STEN MKII, MKIII, and MKVForum Discription: Semi-Auto Build InformationURL: http://www.weaponeer.net//forum//forum_posts.asp?TID=10177Printed Date: March 15 2016 at 8:50am

Topic: STEN Mk II Build

Posted By: blurrededgeSubject: STEN Mk II BuildDate Posted: September 29 2009 at 12:56am

Alright, finally got around to starting a build.I've got alot more done that I have photo's of, but I got so 'in the groove' while working that I forgot the keep taking shots with each step.Here's what I have sofar:Put my AR trigger group into my trigger housing. I made a little box to test my measurements before doing this just to make sureeverything would line up. I'll post pics of that soon.

I know the hammer hole is too close to the dust cover holes, those were welded closed and a dimple ground there so the dust cover wouldstill fit. I didn't take the size of the holes into account when I decided where to mount them.

Trigger before cutting the spring hook off to make the notch for the trigger bar:

http://onclick%3Dwindow.close%28%29/http://onclick%3Dwindow.print%28%29/


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After the cut:

Now, time to make a new trigger bar since I don't want to cut up the old one and it should be easy enough to make. I'm doing alot of things

that make more work for me on this, but I am learning ALOT from the experience, which is worth much more to me in the long run.

This old rusty wrench in the scrap bin is about the right thickness and should be plenty strong. I cleaned it up on the belt sander so I couldapply the dye-chem.


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Next I traced the bar, minus the 90* piece since it won't be needed.

Then I cut it out with the reciprocating saw, and cleaned it up on the grinder and the belt sander.

That's all I have pics of right now, but I've already done most of the work on the tube, including the blocking bar (first thing I did), the mag well cuts, the front trunion cuts , which includs a blocking nub to keep s tandard short barrels from being installed, and the cocking slot, which I moved alitt le higher so a regular s ten bolt wouldn't line up with i t. I also have most of my bolt machined out of a 1.5" bar of 4140, just need to figure out the firing pin.

My major obstacle at the moment is figuring out the best way to ressurect all the machining done after the drill bit for the firing pin hole


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broke off inside the bolt face. I have a few suggestions on how to rectify this, but any other suggestions are welcome.

More pics to come when I can get them.

-------------Semper Fi

Replies:

Posted By: blurrededgeDate Posted: October 01 2009 at 12:21am

Alright, more pics.

In a sort-of order...

Here's the Trigger housing with modified AR trigger, trigger bar, demill hacksaw cuts welded up, and dust cover detent holes welded up with a dimple ground in place t o locate it. Thanks to tricky rick for the guidance on alot of this. I moved my FCG as far forward as I could.The hammer does reach higher into the tube, but with my bolt, it won't be a problem. I just had to make sure that the hammers cockedheight and end of travel would be doable without having to make to deep of a slot in the bolt.

Tabs welded on for the trigger spring. Hard to see, but the inside of the trigger housing was thinned just a tad with the mill so I wouldn'thave to skinny up the AR FCG parts. Cutting the notch where the trigger used to be was bad enough, these parts were Tough!


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Here you can see the denting from testing the hammer/disconnector release (before I realized it was beating up the nose). I had to weld adot on the bottom of the hammer notch to get rid of the gap. If I released the trigger fast enough from the disconnector, the notch wouldcatch on the front, but a slow steady release and it was just enough to miss and fall forward again.

This little box helped Greatly with figuring out how far I could push the limits of the FCG forward and vertically.


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Here's the tube (still some cuts to be made: cocking handle J-hook, trunion weld holes, rear J-hooks for cap)Right Side. Cocking slot has been moved higher than the blueprints indicated so it won't work with a FA bolt.

Top view.

Left Side.


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Bottom. Directly in front of the hammer slot is the blocking bar (large hex key) welded in place. Alittle sloppy, but it was my first real

attempt at welding with the MIG. I placed it there so that: a) The hammer slot cut into the bolt will also clear the blocking bar making alittleless work, and b) the hammer has something harder than the trigger housing to contact incase the trigger is pulled with no bolt in the tube.

Looking down the tube from the rear.

The ejector claw was cut from the same wrench used for the trigger bar.

Trunion fitted to the front of the tube.

For a block to keep a standard short barrel from being installed, I was going to use a length of an old broken punch from the scrap box.


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After figuring out a location and thinking over things a bit, I decided that the cleaned up end of the punch would also make a decent frontsight, so I drilled the hole all the way through and will cut and weld the punch once I have approximated the necessary height of the frontsight off the tube. When drilling the hole in the trunion, I installed my barrel and drilled the ring on that too, which I then cleaned up with anend mill. One bennefit of being able to locate the barrel in the same position every time, aside from consistency with trajectory, is beingable to reposition a feed ramp incase one needs to be made in the base of the barrel.


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Here's the cocking nob I spun next to the original. This was my First use of the lathe... ever.

Here's how it sits in the bolt, and the hole in the bolt for it.


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Here's the trigger housing slid onto the tube.


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Hammer forward as viewed through the cocking slot resting on the blocking bar.

-------------Semper Fi

Posted By: trickyrick

Date Posted: October 01 2009 at 12:29am

is that an original id tube? looking good.

Posted By: blurrededge


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Date Posted: October 01 2009 at 1:29am

Now, about my bolt. As I mentioned earlier, when I was drilling my firing pin hole in the front, the bit broke off. I decided to try to anneal thebit while still in the bolt (hence the coloring), so that it could be ground with small diamond bits in the dremmel, or drilled out maybe. Well,I got the front of the bolt as red hot as I could, and dropped it into a coffee can full of vermiculite (coutresy of work) to slow the coolingprocess.Well, the diamond bits were able to flatten the end of the drill bit after it had fully cooled, but couldn't seem to get any further. So, Idecided, after some advice from 'the old man' (not My old man), to drill from the back of the bolt, just up to the tip of the bit, and thenpunch it out the front.

Here's how the story goes:

The Bolt.

Frontal Angle.

I still have more to trim off the bolt body to get back down to stock bolt weight. Before I made and cuts to the front for the feed lips,extractor slot, ejector slot, and blocking bar/ hammer slot, the bolt was twice the weight of my sten bolt.

Drilling in with the first larger bit as far as I could go without opening up into the deep cuts in the front of the bolt.


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Following up with a smaller bit. The green tape is an approximation of when I need to go Real slow as I'll be getting close to where I guessthe broken drillbit might be (very technical/scientific stuff).

So, here's what happened. The smaller bit went for a walk...


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came through the slot cut for the extractor as well

At this point I accepted the fact that I was going to have to drill the core of the bolt and press a rod in to reshape, so it was time to get thisdamn broken bit out.


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I decided to chuck the bolt in the mill and attack the bit from above and behind.

The results.

The endmill was strong enough to knock the broken tip loose and it popped right out the front hole. I neglected to pay attention to the topof the cutter though, and it gouged the top of the extractor groove badly.


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I chock it all up to learning experience. This project is my introduction to mill and lathe work, and I've learned ALOT.

Here's the bolt before drilling for the insert.

And After.

A shot from high rear, note the light through the now clear firing pin hole.


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Next I'll retrieve the 3/4" 4140 rod, and prepare it the way I SHOULD have done the bolt.

Facing the end of the rod on the lathe.


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and then center drilling it.

I'll end with this shot of the bolt in the tube, since I forgot to add it earlier.

That's all for now. Once I figure out exactly what I'm doing for my firing pin arrangement, I can then drill the rod to the predetermined depthbefore turning it down and sizing it to fit the hole in the center of the bolt. After that, I'll have to recontour the bolt face, the recess for therim, and possibly the extractor and ejector claw cuts. I can't make the fit too tight either or it may push out and distort the very thin metalcurrently on the feed lips. And yes, the feed lips will be cut back with the rim recess once it's reshaped.


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More to come when I get to it.

-------------Semper Fi


Yep, original ID tube. .065" wall, 1.5" OD.

-------------Semper Fi

Posted By: midmichigunDate Posted: October 01 2009 at 8:01am

Blurr

Nice going! I have a Sten project on hold right now.

If you can, let us know what dimensions you are using in all things! I have the SGN article on CD (and paper) on what Mathews did.... I amlooking for other methods.

I will have more questions... but I am at work right now!

Posted By: nachtDate Posted: October 01 2009 at 8:38am

Looking good! You must be a natural with a lathe. I have had my lathe 40 years and I ain't as good as you.

This will not be your last build. It gets in your blood.

Posted By: blurrededgeDate Posted: October 04 2009 at 7:21pm

Got alittle more done. The insert is now welded into the bolt and started reshaping it. I added some weld to the top of the extractor cut where it got gouged by the endmill, since I'm going to need to anneal the whole bolt with the weld so it can be drilled and machined


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anyway. Started work on the firing pin, it's not precise, but it's something to start with.

starting to turn the insert:

Getting there, but still a ways to go.


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Closer:


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Time for some finishing passes. The Old Man gave me another tip. Hold a damp rag against the piece to catch the fine chips and help

polish it. Seems to work okay, but it helps if the cutter isn't getting dull.


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(Normally I use my right hand, but it's hard to take a pic with my left)

Time to trim off the end that held the center:


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Insert is ready for the hole drilled in the bolt.


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Insert welded in, refaced, and recutting the ejector slot.


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I realize there is a large gap in play by play pics, but I got into the groove again, and forgot to take them.

I used the firing pin from my FEG Hi-Power copy to get some dimensions and ideas. Also had some extra FP springs that I thought might work. At the moment, I'm going with a larger spring (not sure what it's from) that slips right over t he 3/16" O-1 drill rod I'm using for the firingpin.


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While waiting for the Bolt to cool, I got some more done on the trigger housing. I like trickyricks idea of welding a bracket to the tube to

screw the triggerhousing onto. I welded a block of 1/4" steel onto the nose, which will also strengthen it against hammer falls. Also weldeda hefty piece of angle onto the bottom of the tube. I'll have to get pics of that next time.

The bolt apparently wasn't drilled on center for the insert, so the firing pin channel and hole that was drilled into the insert isn't centered onthe bolt face. So, I'm going to keep going with this bolt because I really want to get it done for this coming weekend; but I'm not happy withit, and there are things I would have done differently if I had a chance to do it over... experience is the best teacher.

-------------Semper Fi

Posted By: midmichigun

Date Posted: October 04 2009 at 8:35pm

Blur,

Nice work! Seriously, if this is your first go around... you are doing REAL well!

As you mentioned, experience.... but don't fret. I have seen alot of people drilling holes that are long and the bit tends to wander. It is realtough!

Looking forward to seeing this thing shoot!

Posted By: trickyrickDate Posted: October 04 2009 at 9:36pm

blurr, i know how those wandering holes are. i messed up a pps bolt that way. i had a broken bit also, thought i got it all out and didn't. bitdid the same thing, hit the broken one and shot off to the side. glad you could use something i posted, although i'm sure i got it from

somewhere else. keep on going and remember the pics.


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Posted By: bikergunnutDate Posted: October 05 2009 at 12:43am

Nice progress . Didn't the old man tell you to roll up those sleeves . A folded up rag would be less likely to catch.


It's getting chilly up here in New England... was about 39* when I started working that morning. Otherwise the sleeves are usually up...

unless the dremmel or die grinder is sending hot sparks up my arm.

-------------Semper Fi


More Progress.

cutting the feed lips off the bolt face after the rim recess was cut.

Then recutting the extractor groove. (Original bolt present for comparison)


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Seems I had to cut into the firing pin channel anyway after adding the insert.


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Then test fitting the extractor... which is now too long...


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Guess I'll just have to make a new one that's alittle shorter:


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It's getting there, I'll have to final fit it tomorrow. As well as finish up this firing pin with alignment and protrusion, etc.


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Here's some shots of the Mounting block for the Trigger Housing.


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And we'll end todays update with the barrel nut and length of pipe I cut out for the handguard. I've scribed the three lines for the vent holes,but have no data on spacing and size, just photos...

Anyone care to measure their Mk III handguard holes and give me some dimensions?

-------------Semper Fi


The front sight that won't be...

I started welding the front trunion to the tube, along with the front


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sight

Once the trunion holes were filled in, I started building up around the base of the front sight... and got alittle carried away.


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Starting to shape the splats


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...and time to cut and grind it all off because I forgot that the magazine well needs to clear it, and with the trigger group tang welded on thebottom, I can't slide it on the back of the tube either.

This will not be ready for the weekend unfortunately, so I'm going to take a few days off from working on it right now. I've been trying to rushthings and making mistakes, and I want to take a step back before I mess something else up.


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-------------Semper Fi

Posted By: nachtDate Posted: October 08 2009 at 2:46pm

You ain't the first person to make that mist ake. I, for one, normally don't mention it.

Your work is excellent for a 1st build. I do think the front sight was a little tall, but I figured you were not through with it when you caughtyour error.

Posted By: blurrededgeDate Posted: October 08 2009 at 7:19pm

I wasn't too worried about the sight alignment when I installed it, it was "close enough" when I checked it through the 'ol peep down thebarrel and then through the sights trick. Nothing some filing wouldn't be able to correct.

I think to fix this I might drill and tap a spot to screw one onto the receiver, but I have to think about that some more.

New bar for a new bolt ordered today; it'll be a few days before my next update.

-------------Semper Fi

Posted By: blurrededgeDate Posted: November 01 2009 at 11:48pm

So maybe it was alittle more than a few days...

Here's the new stock, the original bolt, and the botched first bolt.

Facing the stock. The stock was just a hair too big to fit through the chuck so I had to face it hanging out, but lucky for me it spun closeenough to true (no visible run out)


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turning down the OD


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Getting ready to cut off the piece.

I could only go sofar with the tool, and the bandsaw was waiting for a new blade, so I put it in the vice and used a hacksaw.


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Then I faced the end I just cut.


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Turned the OD down to final dimensions.


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Then I cut the bolt face recess, using a 6 flute 3/8" cutter.


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That's all I got done last time.

Hopefully wednesday I will be able to get back to the shop before work and do alittle more.

-------------Semper Fi

Posted By: gundoctorDate Posted: November 02 2009 at 12:17am

Great build, photo's, and documentation.

Posted By: blurrededgeDate Posted: November 05 2009 at 12:33am

alittle more work done this morning before work.

got an extension made for the back of the bolt out of a random hunk of pipe... I'm afraid it might be electrical conduit but we'll see how it works for now.


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,Top View

Next it was time to get this firing pin nonsense figured out. I took some annealed 3/16 O1 drill rod and attempted to turn it down in thelathe


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It was flexing under the tool pressure, I could barely make out a visual taper cut getting thinner the closer it got to the chuck.

So, I choked up on it, and figured i would try doing shorter sections at a time.


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I also noticed that the tool was conveniently sharp enough to cut the face of the rod, so I tried working sideways. Instead of cutting the odsmaller and smaller over the length, I would do it across the width, very slowly.

seems to be working, so I brought it out further to do the next segment.


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starting to look halfway decent...

Roughed to shape... just need to touch it up with the files


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all contoured and ready for a polish

Until it decides to snap at the base of the shaft


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I attempted to do it again, but the second time it was tapering way to much, and drawing the tool in as it turned, so there was a drastic

taper in the middle that ended up snapping again...

So I found a good sized drill bit with a long shank and used that instead. here it is with the original bolt (I was comparing the firing pin tips)


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empty head

Filled


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I'm not sure if that recessed area around the firing pin hole will be a problem or not as far as supporting the primer enough so it doesn't tryto pop out.

anyway, I found that the bolt face recess was just a tiny bit too small... so I hunted around through the ''drawer o' mills'' and found one that was just about .400" a hair larger than the sten bolt face recess at .389", so I c hucked it up and started to cut it out alittle bigger.

Here you can see the rim is just alittle too big for the current recess.

preparing to cut it out


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czech-ing the cut, you can see how little it's taking off (red arrow points to the cut lip).

now the brass fits with alittle wiggle room. The extractor will probably take most of that up once it's installed.


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almost forgot, here's the finished firing pin with spring under the bolt and extension tube. I must have forgotten to take a pic of theextension cap I made... I'll put that up tomorrow with tomorrows work pics.

and I'll end today with a quote from the old man"... ya k now, they make these machines capable of m easuring thousandths of an inch for a Reason"


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-------------Semper Fi


Waiting for the dykem to dry.

I'm using a ring of the receiver tube to line up the bolts so I can trace the feed lips and ejector cut onto the new one.


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should be close enough to get in the ballpark

snugged it up in the vice, and found a 3/4" endmill that will take off alot of extra material. Apparently I discovered a 'special tool', accordingto the old man, used for doing something with ratchets (?). I'm not sure what he meant, but it cut a barely visible dovetail shape.


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Time to make the ejector claw cut with the 1/8" cutter


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I ended up snapping the tool, which wasn't in that great a shape to begin with... but it was the only one that size. So, I had to finish it up with a 3/16" cutter. Forgot to take pics during that process though; it would be alot easier if I had a secretary to take the shots and writedown measurements and do calculations for me. I can dream right.

Anyway, I also found a pristine ball endmill (I think that's what it's called) that looked to be the perfect size to finish up the bolt, cutting thefeed lips etc.


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time to cut the other side. At this point I tried the presicion method. Found the center of the piece, then the distance from center that I'dgone to the one side, and went that same distance the other way from center using the thousandths dial. It took a while to get it right until Iremembered I have to take into account half the width of the tool etc.


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here it is all finished up.

Forgot to take pics of the blocking bar slot that screwed me last time by having to remove toomuch material. Since I used a hex key forthe bar, the rounded endmill would still work, and just happened to be the same width. Finding that particular cutter saved me ALOT of

work on t his bolt.


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reminds me of a PPs-43 bolt with the round cutout in the side like that (which is technically, the bottom of the bolt)


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In this last one, you can see where I used the alightly larger cutter to finish the ejector slot. It also went a hair deeper and exposed thefiring pin slot, but there's enough space where it won't be an issue.

Checking my work for clearance on the ejector

and the magazine. It looks close and not centered in the pic, but the mag well was slightly skewed, it lines up great now.


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here's the extension parts for the back of the bolt. still need to get my dimensions nailed down, as that tube is probably a bit long.

And here's a mock up with no guts


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D2Zero is in my reenacting unit, and we've worked on a few projects together.

-------------Semper Fi


Alittle more progress. I will probably redo the extension for the back of the bolt I made because; a) I think it's too flimsy to hold up, so whyrisk it, and b) I also realized that when the bolt recoils in the original version, the bolt is stopped by the rim of the recoil spring cap, not bythe back of the spring guide on the back of the bolt. So, I'm going to make the next version of the extension have a large enough washer todo that, which will transfer the force to the main bolt body via the thicker extension tube. I also ended up with a bolt that's a bit lighter thanthe original, so hopefully a more meaty extension will help get it back to original weight. Not that a few ounces will really matter, but I'drather run as close as reasonable.

Anyway, I'm including this next bit just incase someone out there hadn't thought of it, and it can come in handy. This was done so I couldmill a slot in the bolt extension that I will Not be using, but the tip is still helpful. If you're going to have to make a cut in a piece of roundtube that will get crushed by the vice under too much force, or get jarred loose by the tool under too little vice pressure, a wooden mandrelon the inside will make life easier.I used a cut off length of broom handle because it was the closest to the ID I needed.

it fit tight, but that's good when you're going to need to clamp down on it.


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Here's how it worked, much better than the attempt without it (bottom). The endmill wripped it right up out of the vice once it cut enough ofthe supporting surface away.

After many discouraging failures at fabricating a suitable bolt extension, I took a break and worked on another charging handle, since I also

wasn't satisfied with the first one I made, I wanted i t to extend into the bolt body deeper.Here's the original, the first one, and the 1/2" rod stock that will be the new one.


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Chucked in the lathe and ready for fruition

Turning the rough contour.


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Finishing up the rough cuts. The files you see below will be used to finish shaping it. It's really hard to take a picture when you need bothhands for the tool, and I was doing so well that I forgot to take a final photo. I'll try to remember tomorrow.

I also got the firing pin retaining pin hole drilled, but this is the only photo I have of that since the drill bit broke while going out the other

side. I had to flip the bolt and relocate the hole position since the bit wanted to wander as it hit the firing pin hole. Luckily I was able topunch it out, and then redrill with a slightly larger bit (after finding a new larger pin, which ended up being a roll-pin) to get the hole straightall the way through. The problem with that however, was that it meant I had to cut deeper into the firing pin body to clear the larger retainingpin. The whole thing is made of drill rod, so hopefully I can harden and temper it well enough that it won't create a weak spot or be anissue.


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That's all for today. Hopefully tomorrow will be more productive, and I'll remember to take more pics.

-------------Semper Fi

Posted By: trickyrickDate Posted: November 11 2009 at 2:24am

lookin good blurr


More progress, but yet again, forgot to take alot of pics.

I still wasn't happy with the way the bolt extension was coming out, so I used the one I had originally machined as part of the first boltattempt. (the part Not discollored by annealing)

After doing alittle trimming to get the extension fit right, I pressed it onto the back of the new bolt, and locked the two pieces together inline using the lathe jaws and tail stock. This ensured that as the welds began to cool, the pieces wouldn't warp out of alignment.


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Rotated to see through the hammer slot


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Next I drilled out the center of this big beefy washer I found in the washer bucket.


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Then I took some pipe from a previous attempt at parts match up, and turned the end to slide inside the back of the extension, andsandwich the washer. Put it back in the lathe, cranked in on everything with the tailstock again, and welded the rest up.

My welds are horrible looking, but given that all I have access to is this old MIG, and have little to no real experience trying to weld morethan a dot, well... atleast the welds are holding now instead of popping loose.


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I ended up adding more welds on each side of the washer to provide more support and retention. After everything had cooled enough, Ispun the whole assembly, trued up the extensions, and reduced the washer to fit in the tube just as the the bands on the bolt to add extraalignment and an impact surface.

After re-examining my parts today, I realized my statement in yesterdays post is false: The bolt does Not contact the recoil spring cap,and Does hit with the back of the spring guide. If you take your original bolt, spring, and spring cap, and compress them down as thoughthey were inside the tube, there is about a 1/8" gap between the spring cap bell, and the back of the bolt when it's fully recoiled. However,my bolt was trimmed after realizing this, and so mine WILL contact at that point. I don't think it will be an issue however, except forpossibly having to trim a few coils off the spring so that it doesn't overcompress and get mangled.

Here's the finished bolt with extension; well, I still need to make the cocking knob hole, add the extractor, and mill off the front of the feedlips, but most of the work it done.


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The dyekem was to try and figure out where the bolt might be binding in the tube. Turned out to be rubbing on the side of the ejector claw.Alittle filing from the front cleared that right up.

Speaking of cocking knobs, here's the finished top of the one from yesterday. (right side)

The last thing I started working on today was the hole in the bolt for the cocking knob. The OD of the shaft is exactly 0.5000, which is whyI didn't even touch it with a file. If I drill a 0.5000 hole, and then sand the OD down until it just fits, it should have No wobble to it wheninstalled. I could even chuck the handle in a drill, add some lapping compound, and spin the knob into the slot until it's a perfect fit. ExceptI don't have THAT much time.

Anyway, the bolt band has been scribed where the cocking slot is, and the center of the band located to start drilling. (I will have to cut the

cocking slot alittle further forward, but big deal, it's easier than having a hole that's half way off the rear bolt band).


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Next I broke out the 1/2" drill bit and started the hole. (I remembered to take the pic while changing to the end mill, so I stuck it back in fora quick shot, that's why it's already cut)


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Closer view


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Time to bottom the hole out flat. I went through about 8 different style end mills until I found one that was marked 1/2" and was actually0.4995 across the blade ends... I'm going to assume that the 1/2 mark was referring to the tool shaft size...


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Didn't get any more pics because I lost track of time, and had to change and leave in a hurry to get to work on time. Well, the holesomehow ended up tapered, so I had to spin the bottom shaft of the knob with a file to get it to a slight taper that fit. The cutter was a 4

flute, and so left a nub at the bottom of the hole. So, instead of finding a 2 or 3 flute endmill to cut it out, it was easier to center drill thebottom of the cocking knob to just fit around it.

May not be able to get back to work on this until the beginning of next week, so for MY bennefit, I'll add what I have left to do:

-Extend cocking slot in receiver-Add J-hook to cocking slot. It may not be functional, but it can still look like an original STEN Mk II-Cut feed lips off bolt face-Make new modified extractor-Cut slot in bolt for extractor-Drill hole for Extractor pivot pin-Trim stock keyhole plate for ease of fit in rear of trigger housing-Figure out WTF I'm going to do for the front sight-Function test, and do final tweaking-Bead blast everything and park/paint

...almost there

-------------Semper Fi

Posted By: elmacgyver0Date Posted: November 12 2009 at 7:52am

That is some damn fine work!

Posted By: Dragon2ZeroDate Posted: November 16 2009 at 6:27pm


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Lookin' good, man. Great progress

-------------That'll never work.

Posted By: trickyrickDate Posted: November 17 2009 at 12:26am

looks great blurr


Looks like I'm getting close to done with fabrication.

I decided to finish up the cocking slot in the tube. Had to take alittle more off of the front since my handle hole ended up alittle furtherforward. I also discovered that my cocking knob hole and my slot were not perfectly aligned, so I was going to have to make the slot alittle

wider to compensate, and maybe skinny up the part of the knob that ran in the slot.

Since I was going to tool-up for that, I decided to get the J-hook done as well. It wasn't really going to be functional, but it Would provide aspot for the kocking knob to be installed, And it would add to the historic appearance.According to this template, my j-hook will be back further by about 3/4 inch since my bolt cannot rotate (due to the blocking bar) anyfurther forward of this spot.


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Getting ready to make the cut


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and Making the cuts


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Once we clean it up alittle...


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Not the best way, but the easiest for me, and I won't need to whole block at this time. Make some passes, and then run it on the beltsander once I know the sides are square.


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Fastforward to this dye-kem'd piece of steel with my extractor shape scribed into it.


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And fastforward again to the cut piece compared to the original


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Not too bad for finishing the shape with files, especially for me, I Always end up with cocked surfaces.

Moving right along with that momentum, I located and began to drill my extractor pin hole. I decided it would be easier before I cut the slotfor it than after.


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with the hole center drilled, I'm going to keep drilling with a larger bit down to about 1/4" from where t he ext ractor s lot wall will be, just to tryand keep the hole as straight as possible


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And ten finish it up with the propper sized bit. It took about 20 minutes to drill the hole, since I backed the bit out about every 3 seconds ofdrilling to clear the chips and add some oil. I was NOT going to break this bit... especially since it was the only size 36 bit in the shop...


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The hole isn't perfectly straight, as viewed from the top or the front, but it's c lose enough, and since I'm using a roll-pin as the pivot pin, theextractor will need a slightly oversized hole anyway just to pivot, so that will probably not be a big issue.


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now o cu e ex rac or s o . was us ng a ran new cu er a rep ace e as one ro e, so ec e a ew passes wou e a gooidea instead of trying to do the whole cut at once so I didn't burn up the tool.

Lined up

first pass


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Now, for some reason, the camera went crazy and took the next shot's in 'sephia'... it's back to normal now, dunno what caused it.Anywayz, bottoming cut.


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Since I was trying to keep the same outward appearance, I decided to square off the back of the extractor slot cut instead of leaving itrounded like the side of the cutter, so I clamped it at an angle, and finished the back of the slot like so.


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That's all for now. I was putting everything together, after it was done, and while tapping the firing pin retaining pin in place, the bolt slippedout of my hands, and the extension welded on the back popped off. Probably a good thing to remind me how much I suck at welding. Next

time I'll have to make some practice passes, and then once everything is realigned, burn a bead all around the extension.

-------------Semper Fi

Posted By: dcorbDate Posted: November 24 2009 at 4:57pm

Now I need to build a Sten

Good thing Centerfire has the kits on sale, just ordered one


Save yourself alot of hassle, and just use the original bolt. I could have been done with this thing already if I had done that, but what I'velearned sofar has been more than worth it in the long run.

The only other thing I would recommend, if you decide to go the AR FCG route, is to get the hammer as far forward as possible (even ifthat is beyond the front of the trigger housing) to keep as much room for recoil movement in the bolt as possible. And if you're going tomake the trigger housing removeable, use pins that go in through the side, not the front.

-------------Semper Fi



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a e os e : ovem er a : am

Todays progress:

Last time I was assembling the bolt (tapping in the firing pin retaining pin) the rear extension popped off, my welds hadn't held. So my firstpriority was to clean the two parts up, and then reweld. It appeared that the welds hadn't penetrated enough, probably because the pieces

were cold from sitt ing in the shop. The old man reccommended preheating the pieces, and then welding. I looked up in a copy of an old'welding engineer data sheets' book what the temp should be for 4130, and what the color corresponding to that heat should be on anotherchart600 - 800*f , which would be around "steel gray" after the blue shades have passed, but before the lowest visible red.

Set up in the lathe and braced for welding

Preheated and ready for welding


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After the weld. The pic is blurry because of the exposure time in low light, but it's enough to see the red glow after welding everythingaround. I decided to weld it like torquing on a tire, do one spot, than rotate 2/5 and do another spot. Once the spots were on, I filled in

between them, rotating the same way.


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I let it sit and cool, and worked on some final fitting of small parts like the FCG. Forgot to take pics until I was about done for the day.Anyway, I decided to spin down the exstension and cut out a few hidden spots on the bolt body to get the weight back down to close to

the original; I'd say I got pretty close.

original bolt


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new bolt


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Here's a shot of the final seembly, ready for testing.

Looks much better with the aluminum dummy barrel installed

Initial function test are ok. It feeds fine by hand, the faster I cycle the bolt the better. Extracts and ejects flawlessly. However, I keep


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, , .The forward movement of the firing pin seems fine, unless it's somehow binding... not quite sure what the problem could be unless thebarrel is chambered too deep for the bolt pocket. I'll have to mess around with it more at some other time. I'm not going to even think aboutsandblasting and finishing until I've got it working atleast 99%.

-------------Semper Fi

Posted By: Dragon2ZeroDate Posted: November 29 2009 at 10:42am

WOW - after seeing these most recent pics, all I can say is. ..t hat thing looks simply outstanding...and now I want one, too! ...damn you...

Looking really good, man...really good.

How much does it weigh? How does it handle with that longer barrel?

-------------That'll never work.


Don't have access to it at the moment, it's in the gun closet at the apt right now, and I'm over at the house to help my father put new doorsin. It's heavier than I thought it would be though. The long barrel doesn't seem that wierd to handle because I'm used to long gunsprobably... the corps always made sure I had a rifle, no need for a subgun I guess.

Hopefully I can figure out the firing pin problem and get some reliable function. At this point, my satisfaction with it is about 3 out of 5, butI'm sure once it works 100% and has been blasted and parkerized, that will go up.

-------------Semper Fi

Posted By: InabadhoodDate Posted: November 30 2009 at 9:18am

That's some EXCELLENT WORK!!!

I've seen some nice STEN builds in the past, but I have to say that I REALLY like this one the best!

Great use of alternative materials to come up with your own means of solving a variety of problems! Also, a bit thumbs-up for using sc rap

metals as well!!!

Posted By: blurrededgeDate Posted: December 04 2009 at 12:51am

I was told by 'the old man' and his son (who is old enough to be my father himself) that they were very impressed with my work for havingno training in a trade school or apprenticeship of any kind, and the project was very ambitious for someone who had no real experience

working with a mill or lathe before. W hen he asked me "where'd you learn how to do all this stuff anyway" he was surprised when I told him"I learned it from watching you (for the past 8 years)". The more I think about it, I did learn alot just from reading through all the threads onhere as well, especially the photos. I'm a hands-on and visual learner, without being able to translate the text I read into an image in my

head, I'm lost, and I've always been very mechanically inclined... and I'm proud to have provided you with an entertaining build to follow .It aint over yet though, no sand blasting, polishing, or parkerizing for me until this thing runs 99-100%!

Saturday I will be back at it, and hopefully I'll remember to take lots of pics

-------------Semper Fi


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Posted By: blurrededgeDate Posted: December 05 2009 at 11:56pm

I have no luck with my home made firing pins sofar. After trying to reshape certain areas that cracked and had to be rewelded, the thing was so warped that when the drill bit I was using for the front of the pin s napped where it was welded in, I threw my hands in the air anddecided to just start over AGAIN. but first I needed a break, so I decided to make a split wrench to get the spring cap off easier.I selected a nice thick piece of sheet metal from the scrap bin.

Then measured and scribed onto it for the cuts.


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I found an endmill that was just too big to fit through the holw in the back of the spring cap, and used that to make the cut once therectangle had been cut off of the rest of the scrap. Here it is with just enough clearance to not touch the button that protrudes.


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Sometimes a successful project, nomatter how small, helps you refocus.I couldn't find any more scrap drill bits with a long enough solid shank that were the right size for the Firing pin tip, so I decided to trymachining one out of the O-1 drill rod I still had. I knew I was going to have to make light cuts and could only do about 1/2" at a time or it

would flex t o much.Here's the FP tip shaped.


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The first section turned to the propper OD


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And the next couple sections and cuts


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Success, for the moment. Most of the day was spent getting to this point, and them making another sleeve for the back end. Maybe whenthis one is done, it'll hit the primers hard every time, and my troubleshooting problems will be done... but probably not with my luck.

-------------Semper Fi

Posted By: dcorbDate Posted: December 06 2009 at 8:59am

I am impressed on the Lathe work with the firing pin. Every time I tried to turn something small the results were not something I liked to

talk about.

Posted By: tommerrDate Posted: December 06 2009 at 10:16am

Nice bit of work. All tool steels weld poorly even O1. Drills are M2 and you must not weld them even when they are soft. Even steels like4340 are not recomended for welding because of the nickel. When I make firing pins for the Suomi and the M56, I use O1 for the body ofthe pin and then Loctite a piece of drill blank in place for the actual pin. greg was welding tool steel to make his M56 strikers and theyalways failed at the weld. When I heat treat O1, I heat it red hot and quench the part in oil. ASAP, I stress relief the part at 400F for one

hour AT temperature. It takes a while for the part to heat up so add an extra 1/2 hour. I have never had a firing pin fail and I guarantee themall.

-------------Tommerr


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Good info Tom, thanks! If the O1 does fail, I'll try that method. I need to pickup an old toaster oven that still works from the goodwill orsomething for stress relieving... been thinking about trying to build a small electric oven/forge for heat treating, but it might be easier torebuild a used one that someone is selling.

I'll cross that bridge when I get to it.

I finished the firing pin today, and it works much better than the first one as far as fit and smoothness of funtion. I'll have to take pics of thatand other things when I have time. Still having the light primer strike issue. The hammer spring feels just as strong as the one in my AR

lower... but when I take the bolt, put a shell w/ primer on the end, place that on the workbench, put a punch on the end of the firing pin anddrop a hammer on it from only a few inches up, it strikes perfectly and goes off. So either the hammer spring is too weak, or the hammer issomehow stopped short of the full travel needed.

-------------Semper Fi

Posted By: tommerrDate Posted: December 06 2009 at 8:46pm

Use your kitchen oven for stress relieving the pin. Preheat it to 425F and have it hot and ready to go. After quenching, degrease the pin and

pop it into the oven. Oil in the oven will stink which may cause an argument to ensue.

-------------Tommerr


Will do. I'll make sure to do it when to roommates aren't home.

I just tested the hammer spring using the same test as before with the casing and bolt on the workbench, but held the trigger housing inposition where it would be if these parts were in the rest of the rifle. it took a dozen attempts to get the hammer to hit square and solid the

way I was holding everything, and st ill no ignition, so I s witched back to the punch and hammer and SNAP! it went off. Going to order and

extra power hammer spring from wolf. If that doesn't work, I may need to wind my own (or try making one out of an old rat trap?)

-------------Semper Fi

Posted By: 041xDate Posted: December 06 2009 at 9:40pm

Very nice, I like the pics.


Date Posted: December 06 2009 at 11:23pm

New Hammer spring on the way... hopefully it will do the trick, otherwise I have a bigger problem. Hopefully I won't have to cut the originalrecoil spring down, but it is pretty tight since it's most of the way to full compression already due to the bolt extension. If I were to do thisover again, I would try to find a way to use an offset firing pin that would allow full length use of the recoil spring. The only problem I canforsee is the AR-15 FCG needing to be moved back further than I placed it since it would be lower in the trigger housing. Something likethis:


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-------------Semper Fi

Posted By: blurrededgeDate Posted: December 07 2009 at 10:40am

Realised a problem with the above drawing... there would likely not be enough contact to reset the hammer when the bolt cycles. adifferent FCG may work though, maybe even one from a pistol.

-------------Semper Fi


Well, I will either have to make a new spring, or modify the springs from a rat trap to get it to work reliably. I think my firing pin is heavierthat trickricks, and my hammer is not hitting with the very top, which means there's not as much force from momentum at that point.These are just guesses, but everything else checks out fine. Hammer has plenty of space to move, as does the firing pin, and there's nobinding anywhere... I'm only working security 1 day this week, so I will have time during the day the rest of the week to figure it out.

-------------Semper Fi

Posted By: trickyrickDate Posted: December 13 2009 at 11:48pm

good luck blurr. mine was fine, and still is, except for my fcg pin holes being off. is your return spring for the fp to strong, maybe?


the other thing i had problems w/ initially was that fp was binding in hole of bolt. could that be happening? i looked for spring set up for fp inyour posts and didn't see it. i had to drill from both ends and my holes were off just a bit, but i didn't have your tooling, could that be what'sup?

Posted By: gundoctorDate Posted: December 13 2009 at 11:57pm

blurrd, great work.

Have you considered using a smaller recoilspring/rod like the uzi, AR180, Mac, etc etc. There should be plenty of room in the sten bolt todo this.


I cut a few coils off my FP spring, just incase it was too strong, and it's now VERY light compared to almost every other FP spring I'veencountered. The FP hole is drilled center and true. For the few times that it miraculously DID set the rounds off, it functioned perfectly,extracted, ejected, cocked, and loaded. I took a spent casing, popped out the primer, and melted birthday candle wax into the pocket tosee exactly how far forward my FP was capable of going. It went atleast 2mm into the wax. I did a few more tests using the punch onthe FP with the bolt standing up method, and went from whacking the FP, to barely tapping it. In all cases, the FP did not penetrate theprimer, and in all but the lightest strikes, it left a healthy looking dimple in the primer. In the one or two that did go off from the hammer, thedimple was still very weak. The hammer spring is not being squished inside the trigger housing, and there's no binding happening in thatarea. Next time I'm at the shop, if I don't get it to work, I'll atleast take a bunch of pics for you guys. And if I do get it to work, I'll still take

pics

Gundoc: I had considered that, and if I were to do a custom build, I would most likely go that route. I really like the way the PPs-43 usesthe recoil spring to the side, and the rod is also the ejector, quite clever. For this build, being my first that is not just a pure rebuild (funnyhow a simple select fire rebuild of the original design would have been So Much easier) I wanted to try to stick to as many of the originalparts designs as possible (Without cutting to many of them up).


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-------------Semper Fi


Been going in circels since the last update. When I initially tried the XP hammer spring, it worked, but during later tests, the strike was stilltoo light. Long story short, the whole time, my problem has apparently been two fold. The FP was too short sticking out the back, and myhammer spring was getting caught on the sides of the cut out in the receiver tube. I decided to try and trim the FP in non critical areas sothat it would be lighter, but ended up destroying it. So, I went with Tommers method. I couldn't find any 7/64 drill bits that were very long(apparently that was the size of my FP hole), but I was able to find 1/8" bits 10" long with only about 2" of the front end cut for drilling. I cutoff the front end, leaving about 3/4" of the shank so that it could still be a usefull bit. Used that bit to drill out the FP hole in the front of mybolt, and then used the same bit to drill the end of the drill rod section to be the rest of the FP. Blah Blah Blah, here's a bunch of pics.

I used an e-clip to act as a shelf for the retaining pin to stop against. But, now I need to find a longer spring.

Because I used a 1/8" FP, the hole in the bolt face was too big, which allowed the primer to bubble into it when it fired. So, I used a 1/4"end mill to make a cavity, and spun a 3/16" thick 'washer' plug to fit the cavity, pressed it in, and cleaned it up. It has a 3/32" hole in it, andthe firing pin tip was matched to fit smoothly through it.

Here's the brass showing different stages of testing. Left to right, light strikes, good strike, but primer backing into FP hole, current goodstrikes.


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On a side tangent. I had ordered an inertial buttler pulling hammer, but it still hasn't arrived, so I made a plate to hold the rim, and used vicegrips to grab the bullet and pull it out the top. It mangled the bullet, but I couldn't wait for the thing to arrive. Sacrifices must be made forR&D. In any case, a letter size R and W drills are the perfect size for the inside rim diameter and the case diameter. I just drilled thesmaller hole, then the larger one to the right depth, cut out one side for the shell to slip in, and touched up the taper with the dremmel.

This is the birthday candle melted into the primer pocket I used to see if the firing pin had enough travel at all, or if the hammer spring was just too weak.


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This is the FP sticking out the back of the bolt. I added the ramped area you see because the hammer was not resetting since it wasn'tbeing pushed back down enough. The notch was cut into it to make it easier to line up when reinstalling it so the retaining pin groove wouldbe in the right spot.

However, that ramp needs to be longer to move the hammer back as soon as the gun fires, because at the moment it's keeping the FPsticking out the front for half of the bolt travel as illustrated in these next pics.


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Yes, the FP sticks out about 1/4". I could shorten it, and probably will, but I don't want to take off toomuch and have to start stackingthings behind the drill shank in the pocket. Whatever, I'll deal with that later.


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At this point, the hammer finally starts to be reset and nolonger make contact with the FP, and it starts to reset


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In any case, the gun fired 7 rounds in a row with no problems.

Here's the trigger housing and guts cleaned up and ready for sand blasting.

Here they are mocked up showing how they line up.


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This is the trigger overtravel stop I added, a filed blob of weld.

I may not have time to do more until after new years, but I'll keep everyone up to date.

-------------


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good figgerin out blurr.


Date Posted: January 07 2010 at 12:54am

Attention Tommerr: does it matter what kind (what weight) oil I use for quenching the FP body? is 10w-40 fine?

-------------Semper Fi

Posted By: tommerrDate Posted: January 07 2010 at 10:24pm

The oil quench oil does effect the resulting hardness. Really heavy thick oil produces lower hardness. Light oil results in higher hardness. Itis a function of heat disapaition. A water quench will dramatically decrease the temperature drop time and increace the hardness. A reallythick oil will slow things down a lot. I use automatic transmission oil. It is light, cheap and it works wondeful.

-------------Tommerr

Posted By: blurrededgeDate Posted: January 08 2010 at 12:05am

Thank you sir. I'll give it a shot soon and try to take pics (or have someone else since time may be a factor with quenching).

How hard would you guess the extractor should be? I"m not sure what temperature to temper it at after hardening it. I am going to makethe assumption that it is plain high carbon steel since it came from a large truck leaf spring. I would think they wouldn't bother with a wholelot of alloying since it's a part that will rust, break, wear out, and be replaced quite a few times during the life of the vehicle.

-------------Semper Fi

Posted By: tommerrDate Posted: January 08 2010 at 3:46am

I would be pleased to do hardness checks for you. Most new springs are 6150 steel. I could run a chemistry check for you to verify whatsteel you have. That would require a chunk of steel for some destructive tests. At that point, a piece of steel, that you harden the same asyour proposed spring, would tell the rest of the story.

-------------Tommerr


I have plenty of it. I would greatly appreciate it as I could use this stuff for making alot of small parts. PM me with an address, and I'll sendout a chunk or two, and include those bolts and springs we were talking about not long ago.

-------------Semper Fi


Well, the insert washer thing I put into the bolt face kept working itself loose, so I decided to silver solder it in place.

Here's the washer not fully seated


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Here it is next to the pocket

I acquired some asbestos tape and wrapped it around the bolt head, held in place with some safety wire. The hope was that it wouldmake it easier to heat the bolt face hot enough to get the silver solder to flow without using up all the O2 in my MAPP torch. I wore abreather mask when doing this, yes. Afterwards, the burned tape was placed into a ziplock bag, taped up, and tossed into the hazardous

waste bin at work.


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This crappy pic shows the bolt after the solder had finally flowed into and around the insert. I had to have a friend use my propane torch while I used a MAPP torch to get it hot enough, but it finally worked. The crusty mess on t here is from the flux, but it all cleaned up withthe wire wheel.

I don't have more pics at the moment, but I still need to redrill the FP hole which the solder also flowed into. Hopefully I can get all this little

stuff done soon, but I'm also fighting off a cold, so my next opportunity to work may be filled with sleeping all day

-------------Semper Fi



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Went back to the shop today to finish the bolt face off. I drilled the FP hole, and then went to clean up the back of the hole with a long 1/8"

drill. It was hard to tell when it started to cut, because it went straight through the insert I soldered in . So, I drilled the front out about1/4", and tapped it for a 1/4 x28 NF bolt. Found a small grade 6 bolt, cleaned it up, torqued it into the bolt face, and lopped the shaft off.Then I brought it down flush with the rest of the face with a 2 flute endmill. Redrilled the FP tip hole in the face, and redrilled the same holethe screwed me earlier, this time being carefull not to go too far. Once I was done, I said to myself "that was much easier than all thatsoldering BS, hell that would have saved my original bolt... WHY THE HELL DIDN'T I THINK OF THIS BEFORE!?".Live and learn I guess.

In anycase, the rest of the day was spent sandblasting all the parts in preparation for parkerizing, which I hope to do tomorrow.

Here's the blasted parts:

The bolt was done with glass beads on the front, and the extension was done with 20/40 grit. The rest of the parts, and the two mag bodieson the right, inside, were blasted with 40/80 grit. I ran out after those two mags, and had to switch over to the 20/40 for the rest of themagazines, the barrel, and the floorplates. They were much coarser than I liked, so I cleaned them all up on the brass wire wheel. I alsocleaned up the threads on the barrel nut/ handguard, and the rings and face of the bolt. It will be interresting to see how they turn outtomorrow.

Here's what I've assembled for the task:


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The stainless steel pan is a leftover from cafeteria supplies. The lowly 2 pints of zinc park solution are all I could afford when I bought them,it'll take a while to do small batches, and I'll most likely have to set the pan on a tilt to get the solution deep enough for some parts, but itshould be enough. Papertowels for cleaning the parts with lacquer thinner, and carb cleaner for getting into those tiny areas where I can'treach with a q-tip. Gloves to keep finger prints and dirt off the parts during and after cleaning. The filter and funnel are for when I am done,so I can filter the crap off the top of the leftover solution, and strain it while I pour it into the old windshield washer fluid jug for storage. The

kitty at the top right is not necessary for parkerizingSome things not pictured that I will also be using: Stainless steel hemostat forceps for handling small parts, and stainless wire to suspendparts.

I don't ha

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