Modifying Mk1 Sten barrel nut into Mk2 lookalike

Hi,

Apologies for not posting on here in a while. I do check in regularly, I just haven't had much to report lately gun and bayonet-wise.

However, I have a new mini project... You may recall me expressing in the past the desire to return my 1944 MkV Sten back to it's factory original appearance. Repro foregrips are easy to get (although less easy to fit...) but try as I might I cannot find a Mk2 barrel nut for sale that isn't in the USA.

A Plan B that has previously occurred to me is that you could make a lookalike by adding 3 extra holes to the front and rear of a Mk1 nut. The middle ones would be concealed when the foregrip was fitted.

However, I didn't want to do this unless I could find a scruffy and inexpensive Mk1 nut that I wouldn't feel guilty about irreversibly modifying. On Sunday I finally found one.

Attachment 93245Attachment 93246Attachment 93247Attachment 93248

So I wonder if I could tap into the collective metalworking / gunsmithing experience on here as to the best way of getting 6 extra holes in it that are exactly the right size and exactly equidistant between the existing ones? The challenge is that my kit consists of an electric hand drill and an indifferent vertical drill clamp.

Thanks for any help,
Mark

The most accurate would be a mill/drill and numbered drill bits. Otherwise, freehand and a cross slide vise on the drill press. Numbered bits all the same...

You found one that definitely lay on the sill of the barn for 70 years...

I threw a little thought and Solidworks at this.
Based on your available tools, you need to build a really simple self indexing jig.
I didn't know any of your measurements so this is just a quick 3D sketch but I think it'll get the point across. Here goes.

You'll need a "base" (bottom left), alignment pins (3 items on the right), and of course your work piece.
Attachment 93273

Insert the alignment pins into the work piece:
Attachment 93274

Position work piece into jig, rotating pins until they make contact with the beveled surface, clamp, and simply drill from the top.
Attachment 93275

The angle and location on the beveled surface of the clamp will vary based on the spacing you need. The basic premise though is to simply use the pre-existing holes to locate the holes you wish to drill.

If I can be of any help by modeling anything else, let me know!

Fun little head scratcher to think on while taking a coffee break :thup:

We're making mountains out of molehills here. I'd suggest that yor friend holds the barrel nut, muzzle end doiwnwards on a flat surface while you scratch a line round the circumference level with the centre line of the existing holes. Now repeat with the breech end.
Now measure the distance between the closest edges of the front 3 holes and mark the mid point ON the previously scratched line. Centre punch hard, pilot drill using slow speed drill and then foillow through using correct size.
REpeat at breech end.
Leave holes roughly finished with sharp jagged edges and ignore slight errors to make it look genuine wartime quality!!!!!

I must admit I was thinking more along Peter's lines (with the limited kit and skills I have available) although I'm very grateful to rcathey for his thoughts and Solidworks efforts above. I've yet to go over the nut carefully with a ruler, but I'm hoping the spacings aren't done any more finely than 16ths of an Inch.

I like that idea. Probably what I’d do for myself too.
Working in a production environment like myself sorta requires your brain to think, “ok, how can I make this repeatable thousands of times.” Haha.
It’s a curse, I tell ya!

Have had a play with a ruler and a tape measure and the edge to hole centre length seems to be 6/16 and the centre to centre width across the curve is almost but not quite 1" 9/16.

However, for those of us brought up on metric, the edge to centre is more or less exactly 10mm and the centre to centre width is 40mm.

The hole width seems to be 5/16. I shall probably invest in a proper 5/16 dril bit as an 8mm bit I own is a smidgeon too big.

buy a round copper bar of the right size or turn it down to fit inside, and build up the weld on the holes, cant weld copper

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Originally Posted by philb

buy a round copper bar of the right size or turn it down to fit inside, and build up the weld on the holes, cant weld copper

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You could do, but unfortunately I have zero experience of welding.

I thought I was doing well yesterday when I found the spacing measurements weren't too complicated. However, I've now discovered my drill stand is broken and I need to get another. I've finished cleaning the nut and I have blown some primer on it to help with marking out the holes.

Remember that when drilling on a round surface to use a good hard centre pop mark, a centre drill of if not a centre drill, a small pilot hole first with very little load on the drill.

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Originally Posted by peregrinvs

…………. but try as I might I cannot find a Mk2 barrel nut for sale that isn't in the USA.

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What’s wrong with the ones over here? Are the vendors not willing to repatriate them?

hi, nope, wont send overseas......gun part you know

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Originally Posted by Peter Laidler

Remember that when drilling on a round surface to use a good hard centre pop mark, a centre drill of if not a centre drill, a small pilot hole first with very little load on the drill.

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Thanks. I've never done precise drilling into a thick tube like this before, so all tips gratefully accepted.

I've also been doing some work on the repro grip = reaming out some of the wood so that the ring can move down enough to compress the nut against the grip. Geoff / bigduke6 very kindly added a spacer ring to it last year, but I've now discovered the nut is slightly too big to fit.

So my next interesting challenge is how to shave half a millimeter or so of metal off the outside of the nut without access to a lathe.

I have done a number of the barrel nut conversion from the Mk2 barrel nut over to the mkV nut. The 3 existing holes are easily filled by oxy acetylene welding. Ideally, inserting a 1-3/8 dowel inside will minimize the cleanup afterwards. It does not have to be brass or bronze...steel works fine. The heat required to weld the tube will have no effect on the dowel inside. In the absence of a dowel, the gun's bolt till do.

I like to use a lathe for locating the holes. I find center of a hole, and scratch all the way around the tube to help locate the holes by turning the lathe by hand. Then, using a digital caliper, I find the distance between the two holes, and divide it in half. I set the caliper to that distance, and then use it to scratch the location of the hole between the two existing holes. I like to scratch from both directions, then use the mean of the two scratches to center punch for the hole. You will want to measure each pair of holes, as they are not perfectly distanced.

It is tempting to merely drill from an existing hole through to the other side, but it rarely comes out perfect. and when you are out even by a fraction of an inch, it does stand out. Maybe not to the casual observer, but to you it will, and that should be your harshest critic.

Update: a forum member who is highly knowledgeable about Stens took pity on me and very kindly added the six holes to make the Mk1 nut into a Mk2 lookalike. The very helpful individual concerned also tweaked the spacer ring previously added by Geoff / bigduke6 to make it neatly fit the nut. Thank you to you both.:)

My own more modest contributions were reaming some wood out of the wooden grip to make it functional, staining and oiling it to make it look closer to the original rear grip and painting the grip ring and nut after it had been returned to me. I also took the opportunity to stain and oil the butt which was unissued and a very pale colour.

It's now back to something like it's original 1944 appearance, so I've included a suitable picture of some gentlemen enjoying the successful first half of an airborne adventure in September 1944. I suspect they weren't looking quite so cheerful a few days later...
Attachment 93926Attachment 93922Attachment 93923Attachment 93924Attachment 93921Attachment 93928Attachment 93927Attachment 93925

It's looking mighty fine now...

Very nice!

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Originally Posted by browningautorifle

It's looking mighty fine now...

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Originally Posted by Vincent

Very nice!

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Thank you. And thank you again to the forum members who helped make it possible.

The icing on the cake now would be a dummy bolt that correctly held the return spring and cocking handle + wrapped around the piece of original bolt welded across the ejection port. But that's relatively serious metalworking and will have to remain a hypothetical for the time being. I may however have a go at making a dummy bolt for my Mk4 Sterling SMG that has been deactivated in the same way. That would be a more simple task of adding some slots and holes to a suitably sized piece of metal pipe.

Cracking job, looks absolutely superb, I wish I bought a Mk5 before old spec sales were banned.