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Semi Thompson Mag Catch Question.


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#1 Interrapid

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Posted 11 August 2003 - 08:16 PM

I am working on a friends semi thompson and he wants the mag catch modified so we do not have to cut the hole out on a bunch of original mags. Is this legal to do? My big question is how to get the catch out in the first place. I backed out the pivot plate a little so I can rotate the catch clockwise all the way to the frame and pushed it out about 1/4 inch but the catch spring coiled around the shaft is apparently retained internally. If I pull it out how do you recoil it when installing it? I took out the trigger and sear parts but the catch seems not to depend on these parts. Thanks in advance!
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#2 PK.

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Posted 11 August 2003 - 09:42 PM

After you have removed the Safety, move the pivot plate so the ends of the pins are flush with the side of the frame. Pivot the mag catch far enough to clear the magazine engaging protrusion from the hole in the trigger guard., push on the end of the pivot pin part of the mag catch on the far side while pulling the catch out of the hole. Once the magazine engaging protrusion has cleared the side of the trigger guard, allow the catch to rotate and unwind the spring. Remove the catch. Assemble in reverse.

Duplicate all the contours and angles when lowering the engaging surface .100 to allow use of unmodified GI magazines.

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#3 Interrapid

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Posted 11 August 2003 - 09:56 PM

Thanks, PK. I will try it when I get home tonight. It seemed like the catch did not want to come out more than .25 but I will give it more effort.
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#4 Sgt

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Posted 11 August 2003 - 10:01 PM

Hi Interrapid--
Looks like PK beat me to the punch. I had just written how I do it, but PK's directions are clearer. As far as legalities, no one on this board has reported any restiction against this modification and most of the semi owners have made this fix.
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#5 Interrapid

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Posted 12 August 2003 - 10:04 PM

Got the catch out with the excelent instructions and I think I will jig grind it back tomorrow. Man, there are a lot of burrs on this gun. I am a machinist and would be inbarased if I let a part go out like that!
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