reviskeev Posted September 3, 2020 Report Share Posted September 3, 2020 Hello, I'm new to the Thompson world so please bear with me.I've looked on the internet about the Thompson semi-auto magazine modification. It seems straightforward enough, file off 1/10" from the top of the hole. But I'm able to install the auto mag (the weapon did not have a mag when I purchased it; divorce sell, long story) as is with a little force. Should I be able to even do that? It doesn't look like the mag release has been modified. If the mag is engaging the catch as is then I'm assuming it's sitting high in the receiver causing my jamming issue? Thanks for sharing your knowledge,Reviskeev Link to comment Share on other sites More sharing options...
Oldtrooper Posted September 3, 2020 Report Share Posted September 3, 2020 You can get an unaltered magazine to lock in to a semi auto gun, but it will sit too low to allow cartridges to feed ... If you alter a magazine the bottom of the hole on the magazine needs to be elongated to allow the magazine to sit high enough to feed cartridges. Link to comment Share on other sites More sharing options...
reviskeev Posted September 3, 2020 Author Report Share Posted September 3, 2020 Oh so the bottom of the round holes needs 1/10" took off and not the top? I'm sure glad I asked before I started filing on it. Thanks Link to comment Share on other sites More sharing options...
deerslayer Posted September 4, 2020 Report Share Posted September 4, 2020 Wait... If you are putting a GI mag into a semi gun it's 1/10 off the top of the hole. 1 Link to comment Share on other sites More sharing options...
ppgcowboy Posted September 4, 2020 Report Share Posted September 4, 2020 Better yet modify the mag catch to accept unaltered gi mags. Link to comment Share on other sites More sharing options...
reviskeev Posted September 4, 2020 Author Report Share Posted September 4, 2020 Thanks deerslayer, I thought I saw that the top was what had to be reduced. http://www.notpurfect.com/main/thompson.html#stick Link to comment Share on other sites More sharing options...
deerslayer Posted September 4, 2020 Report Share Posted September 4, 2020 Don't just measure and cut... Cut a little at a time until it just locks up. Push down the magazine follower and stick a punch or something into one of holes to keep it there so that when you fit it you aren't pushing against spring pressure. You want it to just lock into place not dangle low. The same would apply if you are cutting the mag catch. Link to comment Share on other sites More sharing options...
peter kohler Posted September 4, 2020 Report Share Posted September 4, 2020 let dan modifiy your mag catch to use the usgi mags... best way to go and you wont destroy original mags or their value Link to comment Share on other sites More sharing options...
reviskeev Posted September 5, 2020 Author Report Share Posted September 5, 2020 Thanks for the suggestion Peter Kohler. I will reach out to Dan and see what says. Link to comment Share on other sites More sharing options...
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