Sten Mk3 - Stopping barrel rotation

There are quite a few people here in the States building semi-auto Sten guns now that inexpensive parts kits available again. So, I thought I would post a couple of pictures of my solution to the barrel rotation problem.

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As you can see it’s pretty simple. I turned a round bar down so it would just fit inside the front trunnion and then cut a section from it. Cutting down a woodruff key would also work. Then I plug welded it inside the trunnion.

Then I milled a corresponding flat spot on the barrel.

Not much to it really.

That'll work... How were the originals done? Or did the barrel just float and turn?

That'#s a brilliant idea! I wonder why they didn't do it that way.

You got it in one BAR. Literally just float and turn......, almost! But seriously, the original barrels were squeezed between the front and rear collars which were then soft soldered and drive rivetted in place. They usually remained tight for about 6 weeks. There was a modification to tighten the barrels up again which consisted of 4 pronged swageing punch which sort of tightened the barrel up but was also prone to loosening up the front barrel bearing/bush too. So then you had to heat the whole lot up again to allow the solder to re-run and............ and............. But having said that, as a 30 yard bullet squirter it was the ideal candidate to illustrate the saying that you can use the most beautiful walnut stocked and blued £50 Thompson gun or a £2/7/- Sten gun. But you can only kill a man so dead

I was certain you'd know Peter...

As they say, “hind sight is 20/20”. The Mk3 Sten was Lines Bros first real gun. They were toy makers and just didn’t know there would be so much force trying to rotate the barrel. I would have made the same mistake if I hadn’t read Peter’s Sten book.

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Still need to clean up the welds and work on the internals.

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The reduced internal diameter of the tube is intended to prevent a fixed firing pin breach block from fitting. It also makes an original tripping lever too short to trip the sear.

I appreciate that it's after the event and all that but this brilliantly simple idea could have been incorporated into production, in a slightly simplified idea at little or no cost. Just partially punch the centre hole, bend/fold the partially punched section rearwards to form the flat and there it is! Flat across the barrel and......... Where the flat sits radially is academic!

Just wonder why you put the sling loop at the front instead of a pair of holes along the top seam

It's looking good, can't wait to see it high polished and satin blued...

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Originally Posted by Peter Laidler

Just wonder why you put the sling loop at the front instead of a pair of holes along the top seam

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The sling loop was on a section of scrapped casing in about the same position. I just put it about where it was on the original gun. I also salvaged the front sight and part of the seam that has a hole in it.

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Most of the parts are from an SA marked gun. Maybe the Finns added the sling loop? :dunno:

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Originally Posted by browningautorifle

It's looking good, can't wait to see it high polished and satin blued...

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Thanks, Jim.

The casing is made from a section of fence post I found down by the creek. It's a bit pitted in places. I don't think it would blue well.

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Most of the original parts were indeed blued. They are from an SA marked parts kit. Picture to show the contrast with painted.

I am leaning toward paint or powder-coat over Parkerize. Maybe a crinkle like the commercial Sterling guns.

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Originally Posted by Vincent

a section of fence post

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We used to joke about that..."Some old fence post"...usually referring to the inside of the barrel. You might be surprised what a bead blast and blue would produce. I'm sure the paint job will suffice however. Powder coat will do too. Just ask Peter, and Tankie, and Beery...

Today I had turkey, stuffing and all the trimmings… then worked on the trigger mechanism to convert the change lever (FA-SA selector) to Safe and semi-auto.

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A semicircle is cut in the tripping lever so the change lever can pass through it and not move the tripping lever to the side.

When the change lever is in the “A” position the tripping lever is pushed down by the change lever and cannot engage the sear. Thus “A” becomes “Safe”. “R” works as it always had, as repetition or as we say in the States “semi-auto.”

The little block keeps the tripping lever centered so the striker can trip it. More on that later.

Very nice job

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Sometimes things don't come out right. This time the hand guard came out too big. Hopefully the next one will be better.

Better than catching the end of your little finger in the action...

But, as Peter says, you only do it once.

Yep...... And I did it. But only once!

I did the other no-no. Held on to the magazine once. The gun was waiting like a Jesuit teacher with a ruler for just such a mistake. It immediately slapped my hand with a detonation out of battery.

Well done...at least those aren't such a big thing. Just a bit smoky and a bit of shrapnel sometimes. I still have one here in a bag to show the recruits what could happen...

The very best one I saw, as the Range Conducting Officer was with a ruptured case. The front end of which was stuck in the breech. Anyway, firing point supervisor took non firing weapon off soldier, cocked gun, cleared(?) stoppage and then rammed home breech block AND new live round into already obstructed chamber using right thumb and fore-finger.

Live round aligned with recessed breech block due to excess force applied by dozy fart! Round fired while partially out of chamber. Blew thumb back breaking it at joint and sent shower of brass shrapnell into palm of hand. Ho, ho, ho.

He blamed gun and ammunition. I blamed idiot combined with Darwins theory of natural selection

Yes, we had a few of those. My grandfather called them pig headed...