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Guest title ii
Having trouble finding this tutorial also. Is it just the mag catch that must be replaced in order to have the semi auto Thompson use full auto 30 round usgi magazines?
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Having trouble finding this tutorial also. Is it just the mag catch that must be replaced in order to have the semi auto Thompson use full auto 30 round usgi magazines?

No. The mag catches are shaped differently. What is generally done is that the hole in the

magazine spine is modified so that the full-auto mags' will fit the semi-auto mag catch face. This

can be done with a dremel--but don't unless you have a steady hand and know exactly how much to

shave off. A better tool for the beginner is a small round file and slowly removing, checking,

removing, checking, etc, etc. until it fits perfectly. The full auto magazine spine has a hole

and the semi-auto magazine spine has an oval instead. You can modify the hole into an oval but

don't do this with a dremel without expertise. Use the file instead--you are less likely to make

a mistake. But you will need patience.

 

John/T Hound

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Guest title ii

 

 

 

Having trouble finding this tutorial also. Is it just the mag catch that must be replaced in order to have the semi auto Thompson use full auto 30 round usgi magazines?

No. The mag catches are shaped differently. What is generally done is that the hole in the

magazine spine is modified so that the full-auto mags' will fit the semi-auto mag catch face. This

can be done with a dremel--but don't unless you have a steady hand and know exactly how much to

shave off. A better tool for the beginner is a small round file and slowly removing, checking,

removing, checking, etc, etc. until it fits perfectly. The full auto magazine spine has a hole

and the semi-auto magazine spine has an oval instead. You can modify the hole into an oval but

don't do this with a dremel without expertise. Use the file instead--you are less likely to make

a mistake. But you will need patience.

 

John/T Hound

Actually trying to do the opposite of what you are describing above. Presently have a Thompson semi auto with a semi auto magazine catch and want to go to a platform that will allow it to use original 30 round USGI magazines.

Also the modified magazines will be fixed back to factory spec (full auto) once again with welding metal where it was once removed to make it that oval shape.

Edited by title ii
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Obviously such a thing is possible with machining of the

trigger frame to allow it. I am not sure, however, if the

hole position for the mag catch is exactly the same. Kahr

has not allowed the blueprints and specifications to be

published and no one has yet, as far as I know, measured

and presented an informal set of blueprints for such

comparisons. Obviously you will have to compare trigger

frame mag catch positions and hole diameters to accomplish

what you want.

 

T Hound

Edited by T Hound
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Guest title ii

Obviously such a thing is possible with machining of the

trigger frame to allow it. I am not sure, however, if the

hole position for the mag catch is exactly the same. Kahr

has not allowed the blueprints and specifications to be

published and no one has yet, as far as I know, measured

and presented an informal set of blueprints for such

comparisons. Obviously you will have to compare trigger

frame mag catch positions and hole diameters to accomplish

what you want.

 

T Hound

Surly someone has done this modification?

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I modified a Kahr mag catch years ago, I used a dremel tool and some rifler files.

The trick is to lower it .10 of an inch and maintain the original shape of the latch stub.

Be prepared to test fit as you go along.

Darryl

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its best with the catch removed from the frame, a good set of needle files and work the end of the catch as Darryl says 0.1 +/-and maintain the outside radius on the top of the profile, it will look like a circle squashed when finished, no work is required to the actual frame and I recommend getting a replacement catch so you can go back to original should the need arise.

 

remove material in stages and test fit, to test you can remove the spring to make it easier until you get close,

 

good luck

Edited by laurencen
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laurencen,

That would be a tenth of an inch or .10" (+-)

Darryl

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The guys above are correct; mold the catch into a flattened circle, either using a Dremel or file. Take your time, because you'll have to do it a little at a time, re-assemble, check, and repeat until the mags lock firm; it might be good to pick up a spare, as they aren't that expensive. If you go too far on the modding, the mags will wiggle and become loose...I've seen them fall out during use, if the catch isn't modded correctly, so I stress again, take your time.

I'm not sure what happened to the tutorial, but here's some before and after photos of mine:

Before
http://img.photobucket.com/albums/v629/ghostsoldier/My%20Impression%20stuff/My%20Weapons/BEFORE1.jpg

Before
http://img.photobucket.com/albums/v629/ghostsoldier/My%20Impression%20stuff/My%20Weapons/BEFORE2.jpg

After
http://img.photobucket.com/albums/v629/ghostsoldier/My%20Impression%20stuff/My%20Weapons/AFTER1.jpg

After
http://img.photobucket.com/albums/v629/ghostsoldier/My%20Impression%20stuff/My%20Weapons/AFTER2.jpg

After
http://img.photobucket.com/albums/v629/ghostsoldier/My%20Impression%20stuff/My%20Weapons/AFTER3.jpg

After
http://img.photobucket.com/albums/v629/ghostsoldier/My%20Impression%20stuff/My%20Weapons/AFTER4.jpg

Hope these help. :)

 

Rob

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Guest title ii

OK, this is excellent.

 

Does anyone have a tutorial for converting magazines back to original USGI spec's.

The hole on the rear of the 30 round magazines has been drilled like an oval and the goal is to bring it back to factory spec. It would be great to see photos of the actual welding process used to achieve this.

If you have the skills to do this repair and are interested send a PM.

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Most people don't...the steel is too thin, and if you try to weld up the hole, it usually warps.

 

The best bet is to throw them out (or, keep them for parts), and just buy USGI mags. I've seen them in the past for as cheap as 3 bucks each (I bought about 10 from Tapco a few years back, for that price).

 

Rob

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  • 2 weeks later...
Guest title ii
Back to the mag catch for a second just to make sure I understand. The only part that must be modified is the mag catch and nothing else to get the original USGI magazines to function ok. See the attached photo of what the before looks like. Edited by title ii
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