9 replies to this topic

[DGinGA]

Last week I fired my ‘21 with factory brass case ammo in 30 round mags.  With 3 out of 4, the gun would fire one round. The bolt would strip a round from the mag but not feed it. Instead it would close on the unchambered round. This happens with the first 3 or 4 rounds. After that it functioned perfectly. No feeding problems with drums or 20 rounders. If the gun is supported by pushing up on the magazine, it is fine. Thought the issue is bad mags but some are new and all are in good shape. My assumption is the mag catch is worn. 
Any thoughts? Are Thompsons finicky about magazines?

[mohawk64]

You may have gotten some west Hurley modified mags. Please post pictures of the hole for the mag catch.

[Ryo]

Oval is bad, circles are good.

[JimFromFL]

Post images of the hole in the mag.

Also, hold/push the mag from the bottom when shooting. Does it work then?

[TD.]

Since the gun runs fine with 20 round magazines, the problem is most likely in this batch of 30 round magazines you have. As stated above, review the advice about the magazine catch holes.

 

Two questions: 

1. What brand(s) is the 30 round magazines giving you the problem.

2. If this problem occurs when using a GI frame on your Colt's, install the Colt's frame and see if the problem goes away. 

 

I would be hesitant on changing the magazine catch at this point. 

 

Will we see you at the TCA Show & Shoot this year?  

[john]

I had the same thing happen in one of my 28's years ago.
New mags ran with 24-25 rounds but not a full 30.
Some old 30 rounders worked just fine.
Problem was that these mags were properly scrubbed on the outside but inside still had grease adding friction to the follower.
Also ran into same problem with really dirty mags.
I disassembled and scrubbed out the grease and they functioned flawlessly.
HTH.

[DGinGA]

Thanks to everyone for excellent advice. Most of my mags are Seymours; a few are unmarked. The holes are mostly roundish but two are oval. Once I get a camera with macro capability and figure out how to post images, I’ll put up pictures. John’s post is especially relevant: I thought inner lubricant was good but can see how there could be too much or it could be congealed. Time for some binge watching with a mag cleaning/disassembly session. Glad the consensus view is not to change the retainer. I’m not brave enough to risk damaging my expensive Chicago piano by ineptness.

Will be at the Thompson Fun Show & Shoot in May and the ‘official’ one in September.  The ammo cost factor gave me pause; with factory 45 going for $2.00/round, a weekend of firing at least 500 rounds is costly, but recently pricing is improving. Besides we FA types know the economics. If cheap shooting is one’s goal, there’s always air guns.

[TD.]

Unmarked 30 round Thompson magazines? Interesting. Are the unmarked 30 round magazines the ones with the oval holes?

[TSMG28]

The unmarked 30 round mags are likely the current ones from Kahr. Theirs have both ends of the backstrap edges welded over rather than open like all Colt and WWII mags. If you have Kahr mags, the hole will be round, but it will still be located for the semi guns, in the same wrong place as those with the oval hole. Any mags intended for use with Kahr or West Hurley semi-autos will not work properly in standard full auto guns.

Go with WWII 30 round mags with the round mag catch hole and clean interior, with only a light coat of oil. They should work fine.

[1921A]

Oddly enough, almost all the feeding problems Ive encountered with original Thompsons, and there werent many, involved XXX magazines, some of them fresh from the wrapper. XX magazines seem to work even with dents and bent up feed lips.

I let a friend shoot a Savage 28 at the KC jungle walk a few years back. He used 3 new Seymour XXX magazines and 2 well used XXs. All 3 XXXs had repeated failures to feed and both XXs worked fine. Not much fun for a new Thompson shooter. It was the 30rd mags - gun worked flawlessly with the XXs.