Sten Mk3 - Stopping barrel rotation

[Vincent]

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.

Attachment 58198Attachment 58199Attachment 58200

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.

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[browningautorifle]

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

[Peter Laidler]

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

[browningautorifle]

I was certain you'd know Peter...

[Vincent]

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.

Attachment 58209

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

Attachment 58210

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.

[Peter Laidler]

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

[Vincent]

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

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.

Attachment 58256

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

[browningautorifle]

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

[Vincent]

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

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.

Attachment 58257

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.

[browningautorifle]

a section of fence post

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...