Thompson Drum Question

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Buggy Man
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Thompson Drum Question

Post by Buggy Man » Thu Jan 10, 2019 12:58 pm

Guys

I have a 50 round drum for one of the Auto Ordnance semi auto Thompsons made back in the late 1980's early 1990's. Will that drum work with a real F/A M1928A1 Thompson?

Thanks,
Matt

Cal.Bar
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Re: Thompson Drum Question

Post by Cal.Bar » Thu Jan 10, 2019 3:20 pm

Well, I can now definitively answer this question. I actually got to spend some range time (here in CA no less) with original 1921 AND 1928 full auto Thompsons. I brought my Semi-auto Auto Ordinance mags and drum to use. And.... NONE of them work with the originals. They do not lock in and cannot be used with the originals. I have no idea why they would do this but they did. But... with the original mags.... I can report that BOTH were awesome.

GUNNUT in Iowa
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Re: Thompson Drum Question

Post by GUNNUT in Iowa » Thu Jan 10, 2019 3:59 pm

The semi-auto Thompson has a completely different "upper". If I remember correctly, it is not as "tall" as the automatic version.

You can use the automatic magazines in the semi-auto, if you modify them. You must make the magazine retention hole in the magazine into an oblong shape. This will allow the magazine to sit lower and thus let the weapon function.

I have modified a bunch of automatic magazines like this to work in my semi-auto gun. This was back in the day when automatic magazines were cheap enough to do so.

Drum magazines - both semi-auto and automatic - were never cheap enough for me to try the modification. I don't know, if it would work anyway.

I do know that I am always interested in finding drums for my semi-auto.
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Urban Camo
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Re: Thompson Drum Question

Post by Urban Camo » Thu Jan 10, 2019 7:43 pm

Cal.Bar wrote:
Thu Jan 10, 2019 3:20 pm
Well, I can now definitively answer this question. I actually got to spend some range time (here in CA no less) with original 1921 AND 1928 full auto Thompsons. I brought my Semi-auto Auto Ordinance mags and drum to use. And.... NONE of them work with the originals. They do not lock in and cannot be used with the originals. I have no idea why they would do this but they did. But... with the original mags.... I can report that BOTH were awesome.
Strange the drums work in my semi auto.
Only stick mag's needed to be modified to work in S/A version.

Raymond Smith
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Re: Thompson Drum Question

Post by Raymond Smith » Fri Jan 11, 2019 7:06 am

My experience was that the drums will fit in the semi auto version and the auto versions.
The drum hangs on rails machined in the upper frame, while the stick magazines are secured by a catch on the lower frame.

For the semi auto, the magazines need to have the hole in the back of the magazine elongated by 0.10" so they will work.

Glad you had a good time! not sure how you managed that in CA, must have been a movie set,
Raymond
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jonsm114
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Re: Thompson Drum Question

Post by jonsm114 » Fri Jan 11, 2019 6:06 pm

we don't modify the mags locally, we modify the mag catch to hold and lock up unmolested Thompson mags.....on the semi thompsons...

Jon
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Cal.Bar
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Re: Thompson Drum Question

Post by Cal.Bar » Fri Jan 11, 2019 6:15 pm

Raymond Smith wrote:
Fri Jan 11, 2019 7:06 am
My experience was that the drums will fit in the semi auto version and the auto versions.
The drum hangs on rails machined in the upper frame, while the stick magazines are secured by a catch on the lower frame.

For the semi auto, the magazines need to have the hole in the back of the magazine elongated by 0.10" so they will work.

Glad you had a good time! not sure how you managed that in CA, must have been a movie set,
Yeah, it was nothing short of a miracle to get range time in CA with so many full autos in private hands.

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Re: Thompson Drum Question

Post by Buggy Man » Sat Jan 12, 2019 3:21 pm

As my original post stated my question was about weather the DRUM mags from the S/As would fit/work with the F/A guns and that was answered. THANK YOU. I too had to mod a few F/A stick mags to work in my S/A when I had it way back in 1992. Original mags were cheap & all over the place back then. Not so much the case anymore. Now I think I'd do what Jonsm114 did and mod the mag catch on the (original)Thompson mags.

One of my reasons for posting the above question was that I've kind of been bitten by the Thompson "bug" again and have been giving (semi)serious thought to buying another. I know I'll never have the kind of money it takes to buy an original F/A one so a S/A copy will have to do. As of this typing, I'm not sure if I should do another M1928 or maybe buy the M1 this time around. The M1s will not accept the drum mags. On the plus side, I've never owned an M1 whereas I have owned an M1928...



If I do get another Thompson it's either going to be SBR'd (have a friend who's a class-3 dealer) or I may buy one of the blank fire only barrels for it. Only problem with the BfB is that it turns said Thompson into "the world's greatest cap gun" and I like to shoot live from time to time.

Matt
Last edited by Buggy Man on Sat Jan 12, 2019 5:49 pm, edited 1 time in total.

jonsm114
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Re: Thompson Drum Question

Post by jonsm114 » Sat Jan 12, 2019 5:34 pm

The mag catch fix is the way to go..dont destroy the mags.....

Jon
M3 37mm Cannon Parts and Resin Weapon Replicas. We also manufacture reproduction Stuart parts.
Fuel tanks, Rear Exhaust and Air Deflectors, and other components.
314-703-9710

Buggy Man
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Re: Thompson Drum Question

Post by Buggy Man » Wed Feb 27, 2019 5:54 am

jonsm114 wrote:
Sat Jan 12, 2019 5:34 pm
The mag catch fix is the way to go..dont destroy the mags.....

Jon
How does that work Jon? Will an original catch fit in a S/A frame? I ask because I just brought a bunch of stick mags for my future Thompson and I'd like to keep them original and not have to modify them.

For what it's worth I'm going with the M1928 (M1927A1) SBR so I can use my drum mag.

Matt

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Re: Thompson Drum Question

Post by jonsm114 » Wed Feb 27, 2019 8:38 am

The catch is made a bit out of spec on the semi guns. As I recall, the hole in the mag is relieved at the top to fit the semi weapon. the top of the catch is filed or sanded off to allow for the catch to enter the unmolested hole in the magazine....will verify...my cell is attached. 314-703-9710.
M3 37mm Cannon Parts and Resin Weapon Replicas. We also manufacture reproduction Stuart parts.
Fuel tanks, Rear Exhaust and Air Deflectors, and other components.
314-703-9710

dantheman
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Re: Thompson Drum Question

Post by dantheman » Wed Feb 27, 2019 9:10 am

The mag catch on a semi auto Numrich/West Hurley/Khar Arms Thompson is literally no different than that of a FA version. In fact, on early production semi autos original mag catches were used. The issue with having to modify the magazines has to do with the fact that the receiver is 0.100" less tall in relation to the frame rails to the top of the bolt cavity in the top of the receiver. As a result, the distance to the top of the magazine well where the feed lips of the magazine come to rest is 0.100" shorter relative to the lip of the magazine catch. That is why you must elongate the hole in the magazine.

As others have pointed out, it is best to remove 0.100" of material from the lip of the magazine catch to preserve original magazines. Care must be taken to maintain the original shape of the lip once you have lowered it. Lots of times I hear people recommend that all that is necessary is to replace the mag catch with an original one. This is NOT going to fix the issue, the problem will be the same. The mag catches are all the same, the design of the receiver is what causes the fitment issue.

Modern production drum magazines should work in both SA and FA. The drum engages two slots in the receiver eliminating the issue described with the magazines. The mag catch locks the drum into place laterally as opposed to vertically. With that said, I have heard that the newer production drums leave a lot to be desired in terms of quality and reliability compared to original C and L drums.
-Dan

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jonsm114
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Re: Thompson Drum Question

Post by jonsm114 » Wed Feb 27, 2019 10:54 am

thanks Dan......I knew the fix was in modifying the catch, not the magazines....but I learned something today. Thank You.....

So many people get all riled up when someone is advocate for modifying the catch. Something that makes no sense to me is using a dremel tool on the mags.

Jon
M3 37mm Cannon Parts and Resin Weapon Replicas. We also manufacture reproduction Stuart parts.
Fuel tanks, Rear Exhaust and Air Deflectors, and other components.
314-703-9710

dantheman
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Re: Thompson Drum Question

Post by dantheman » Wed Feb 27, 2019 11:00 am

jonsm114 wrote:thanks Dan......I knew the fix was in modifying the catch, not the magazines....but I learned something today. Thank You.....

So many people get all riled up when someone is advocate for modifying the catch. Something that makes no sense to me is using a dremel tool on the mags.

Jon
I was just trying to clear things up. This subject gets discussed quite a bit and sometimes the actual solution gets a bit skewed.

I agree that taking a dremel to original magazines makes no sense either. But, at the same time, a dremel can quickly ruin a good mag catch. Or any other gun part. I’ll take some pictures of mine if anyone is interested to show the profile. Slow and easy is the process, checking the fit often with several different mags.


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-Dan

1945 GPW 267188 (numbers matching)

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