Thompson SM Stock Mod

[James Combs]

A height challenged friend of mine bought himself a Thompson Sub Machine Gun(set for only semi operation) and could not reach the trigger comfortably with the gun held to his shoulder. He asked me if I could shorten the stock for him. Of course I can never say no to odd projects and I said "sure I'll give it a shot. Here are some pics of the process and the results.

Note that he did not want to modify the original stock so he had ordered a replacement off the web and a complete set of associated hardware, a butt plate, screws etc. He wanted 1.5 inches removed but we noticed that the new stock was already 3/8" shorter so we settled on shortening it by 1 inch. Both stocks are very nicely figured Walnut.

I mounted the stock to a sled like setup. A couple pieces of scrap ply glued and nail at a 90* angle. This kept the stock mounting area orientated properly to the band-saw blade and sander drum. The second pic shows the 1" scribe line and the 3rd shows the marked section sawed off.
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The stock flared somewhat away from the butt plate requiring re-tapering to the butt plate outline.
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This shows a comparison of the new stock to the original.
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The stock did not fit the gun when received, the slot that mated with the lower part of the gun receiver was about 0.010" to 0.015" too narrow and we were afraid we might split the stock if we forced it so I shaved the sides of the slot slightly with my table saw blade, again building a sled like jig to hold the stock in the proper orientation for shaving the sides.
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Continued in next post.

[James Combs]

I know most gun folks us Tru-Oil as their gun-stock finish but I used Watco Natural Oil finish. I applied 4 soaking coats and then rubbed it out with 4-0 steel wool.
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There is a special tool needed to change the drum style magazine and he wanted one stored under the butt plate of both stocks. The first pic is the original stock. I chiseled a relief in the butt area and added a little foam pad to keep it from rattling. The second pic is the new stock which came with a ~7/8"x 5" deep hole so I made a foam carrier for the tool and stored it in the hole. The wire allows it to be pulled out of the hole.
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This is a comparison after finishing the new stock.
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Some pics of the finished stock.
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Thanks for looking
C&C appreciated.

[Jim Becker]

You did a nice job on that project!

I'm also guessing that your friend did a very wise thing by obtaining an aftermarket stock for you to use...someday, he may want to sell it and being able to restore it to original configuration could be important to value.

[Will Boulware]

Very cool! Thanks for the walkthrough. Always interesting to see how people handle working with tough shapes like that.

[Bruce Page]

Clever jigs & excellent results. Nicely done!

[Scott T Smith]

Nice craftsmanship! BTW, that tool is called a "third hand" and shipped with the post war TSMG's made by Numrich and Kahr. It's purpose is to hold the semi-auto bolt back so that the drum magazine can be removed (otherwise it is difficult to hold the gun, hold the bolt back, and hold the drum!)

It's not required on the full auto models since they shoot from an open bolt.

As a point of trivia, your replacement stock was manufactured for a full auto TSMG. The 7/8" x 5" deep hole in the end of the stock was used to hold a small oil can (about 1/2" square for the 1921 and 1928 models, and round for the late war M1 models). The metal butt plate on the full auto models had a small trap door in it to allow access to the oil can.