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Posted: 2/8/2026 9:01:26 PM EDT
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I've decided that I'd like to SBR the gun to look like the M1A1 submachine gun. I just want that look. Mechanically is there anything that I'll need to be aware of? Special tools? Can I do this with out a machine shop, etc? I've built a half-dozen AR's but they are cookie-cutter easy. I'm at the very beginning of the process and I've not even begun to fill out paperwork. Thanks. |
'' THE STRONGEST REASON FOR PEOPLE TO RETAIN THE RIGHT TO KEEP AND BEAR ARMS IS,AS A LAST RESORT,TO PROTECT THEMSELVES AGAINST TYRANNY IN GOVERNMENT.'' THOMAS JEFFERSON
"You skunk-haired motherfucker." TEETER
"You skunk-haired motherfucker." TEETER
| If I already owned a 16” version, I’d sell it and buy a factory SBR . |
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I looked into getting a shorter barrel for mine 20 or so years ago. I never did it - everyone I asked - said it was an absolute bitch to rebarrel. I took that to mean I should take the money and go but another something :) Just found this...  1927 Thompson Barrel Removal |
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Breaking the barrel loose for the first time may likely be way harder than in the video. People have run into very difficult threadlocker. Also be aware that the Kahr/W.Hurley threads may not work with a USGI, or aftermarket barrel. Go over to machinegunboards.com, & do some reading. Those guys live, & breathe Thompsons. |
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I'm thinking it might be a wise move to sell and then reinveste in a factory produced version. Mine is unmolested, very low rounds, has the plastic case and extr mags. If I could recoup the money that I have in it I'd be okay with that. The extra effort to remove the barrel looks to be quite a lot and my guess is there is a good chance of tweaking the receiver. WECSOG and all.  Thanks for the opinions and options. |
'' THE STRONGEST REASON FOR PEOPLE TO RETAIN THE RIGHT TO KEEP AND BEAR ARMS IS,AS A LAST RESORT,TO PROTECT THEMSELVES AGAINST TYRANNY IN GOVERNMENT.'' THOMAS JEFFERSON
"You skunk-haired motherfucker." TEETER
"You skunk-haired motherfucker." TEETER
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Originally Posted By pavil58ar: I'm thinking it might be a wise move to sell and then reinveste in a factory produced version. Mine is unmolested, very low rounds, has the plastic case and extr mags. If I could recoup the money that I have in it I'd be okay with that. The extra effort to remove the barrel looks to be quite a lot and my guess is there is a good chance of tweaking the receiver. WECSOG and all. Thanks for the opinions and options. Just send it to Dan Block (over at machinegunboards). He does it for a living, and is fast, and reasonably priced https://thompsonstocks.com/ |
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Dan Block did the barrel swap on mine and I had him do the easy change mod. The mod is just adding a set screw to the bottom of the receiver and a dimple added to the barrel. There used to be a site called thompsonbarrels.com but that looks to be defunct. Need to send out my factory barrel to get chopped and threaded for a can. The shorter barrel greatly helps the balance but it is still a pig. Always a crowd pleaser though. |
What's the worst that could happen?
I had Deerslayer aka Dan Block do my Thompson SBR as well. Be aware though, that YOU will need to actually make the SBR before you send it to him regardless of an approved form 1. Otherwise it would be him that would be making the SBR - which he can't do. So since I didn't have the ability myself to remove the barrel, he said that once I had my approved F1, I'd literally need to cut the 16" barrel to SBR length before shipping it to him so that it was already a SBR.  |
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Originally Posted By ScottXD: Need to send out my factory barrel to get chopped and threaded for a can. This is the move. I had morgan@class3machining do mine. He chucked the whole barreled receiver in the lathe. Chop, crown, thread as well as machine the barrel down to push the rear sight back. Before me, he had done a handful of them on a contract. I think I saw his end up in a silencerco package that was sold at brownells or something like that. 
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