Magazine catch removal

[Steve45]

I am considering replacing my mag catch on my newer 1927 with the old-style mag catch.  I am going to purchase a couple of original 30 round Seymour USGI mags and don't want to file the holes on these original mags, but change the mag catch instead. My question is.......Can the mag catch be swapped out simply without removing anything else on the lower frame? Also, I had Deerslayer install the full auto switch for the bolt hold open and I am also wondering if changing the mag catch would hurt or change anything with the bolt hold open modification?   Thanks for any input in advance.  I am also considering the FRT after it has been perfected and is fully reliable with all upgrades needed to make it work. 

[SparksNArcs]

The mag catch alone won't enable the use of USGI magazines, the round protrusion on the front of it has to be filed down by about 0.1" to match the lower height of the Kahr receiver; using a USGI mag catch is just nicer because the Kahr one is a cheap (cast I think) part. 

From the FAQ:

The magazine catch must be modified by lowering the lip that engages the magazine .100" while maintaining the original contours and shape. This is commonly achieved with a Dremel tool or files. After you have removed the safety, move the pivot plate so the ends of the pins are flush with the side of the trigger frame. Pivot the magazine catch out 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, carefully allow the catch to rotate and unwind the spring. Remove the catch from the trigger housing . (Assemble in reverse.)

 

When reshaping the magazine catch, you must duplicate all the contours and angles when lowering the engaging surface. Removing .100" will allow use of unmodified GI magazines. Be careful not to remove too much metal. You may have to refit and test several times to achieve the optimal shape.

[Steve45]

Thanks for the info. So, the original USGI mag catch needs to be ground down .100" to fit the USGI mags, that being said, couldn't I modify the mag catch already on the 1927 firearm and forgo replacing it? 

[68coupe]

If it were me, I would get a second mag catch to modify, so that it can be returned to original configuration, if so desired. Keep your options open. Ultimately, it's yours, do what you like.

I modified a bunch of magazines, which I now regret doing. It was also a lot more work, doing 15 mags vs. doing ONE mag catch.

Just my humble opinion, Karl

[Merry Ploughboy]

One of the more gut wrenching things to see in the Thompson world are 20 round patent date magazines that have had the mag catch hole enlarged for semi Thompson use.

MHO, YMMV, etc.

[SparksNArcs]

I just modified my existing Kahr mag catch, it was easy to do once it's out of the frame.

[ppgcowboy]

Please modify the catch and not a world War 2 relic. You are on the right track.

[68coupe]

26 minutes ago, ppgcowboy said:

Please modify the catch and not a world War 2 relic. You are on the right track.

I second that!!! I regret to this day that I F@#$%%ed up 15 original mags.

Karl

[Steve45]

Thanks for all of the input, I'll modify my KAHR mag release and buy an old original mag release as an extra for my newer mags in case I want to go back. I believe the original mag release was better quality than the newer 1927 KAHR mag release anyways.

 

[Merry Ploughboy]

I believe that the ProMag 40 round, polymer Thompson drum is not compatible with a reduced height magazine catch.

MHO, YMMV, etc.

[Steve45]

No worries there. I don't plan on using plastic garbage on a Thompson, just the real steel made for a classic, as it is meant to be.....lol...

[Merry Ploughboy]

1 hour ago, Steve45 said:

No worries there. I don't plan on using plastic garbage on a Thompson, just the real steel made for a classic, as it is meant to be.....lol...

I got one of the ProMag 40 round Thompson drums - "last one in stock/close out" - for a ridiculously low price.  I've yet to use it, and I've had good luck with one of their 9mm Glock drums and a few of their .22LR drums, so I figured, "What the heck."  And I've got five steel Thompson drums, four 50s and one 100, so if the ProMag fizzles, no big deal.