I've posted here recently about my friend's newly acquired Thompson M1.  He has 2 50 round drums that don't fit in the M1 version and would like some 20 and 30 round box mags.

Anyone know who the preferred contracters were for these mags?  I'm guessing there are different "makes" of these mags, just as there are for AR15/M16 mags.  FWIW, he wants the equivolent of the better  USGI AR mags (LaBelle, etc.).  I'm trying to steer him clear of mags that are "USA" quality.

Any help on stampings, contractors, etc. would be greatly appreciated.  Links to reputable sources for 90+% or NIW mags also being sought.

Finally, I've read ads for "surplus Thompson mags modified to fit the semi-auto Thompson M1."  Are modifications necessary to the "USGI" mags for them to fit M1's?

TIA

PS  Anyone heard when/if the main AR15.com UBB board will be back up?

Finally a subject I know something about.  All Thompson mags I have ever seen have been "USGI" types except for the pre-WW2 mags which were Auto Ordnance contracted mags and are as good or better than military.  The military mags you will most see are Seymour Products, which can still occasionally be found NIW.  Other manufacturers are Crosby, SWCO, W.P.S., "U" (Universal), Auto-Ordnance (contracted but usually Universal) and Blank ones.  All are fine mags but usually Thompson mags are in widely varying condition due to the fact they usually saw a lot of service and I believe the last contract for mags was let during WW2.  I have not seen any aftermarket Thompson mags.  The pre-war mags are collector mags, especially if the Blank model, and should not be used as the value is too great.  Colt made the first Thompson mags as they made the original guns.  The wartime Blanks are no more value than the other wartime production mags.  Production on all wartime Thompson mags ran WELL into the multi-millions.

For the semi-auto Thompson, the catch hole at the back spine of the mag has to be elongated (toward the top of the mag) because the lower receiver on the semi's are 1/10" shorter. The hole has to be elongated about that much.

30 rd mags are by far the predominate mags but 20's can be had also.  I think Cheaper Than Dirt and other surplus places sell Thompson mags, also Auto-Ordnance does too, already modified for semi's.

Look for mags that have the feed lips in decent shape as this is the week point on Thompson mags. If they are deformed feeding will not be good, although a Thompson is a very reliable feeding weapon.

The drums don't fit in the M1? I thought it was the same except for the wood. [>:/]   Well, anyway, Seymour mags are sought after. Auto-Ordnance works fine. I also have some marked SWCO. You can find mags on auction sights (even eBay) for $15-20. Lots of surplus stores have them. The auto mags have to have the latch hole reamed out to fit. Very easy to do. Some sources offer them already reamed and refinished. I have yet to find a surplus mag that didn't work.       [heavy]

Thanks guys.

The M1 did not have the slot for the drum machined in the receiver.

By the time the M1 came in to being, the stick mags were prefered over the rattling and otherwise noisey drums.

Well, Jac, think all your questions have been answered. But if you still have problems after dremelling the mag catch hole, take a file to the rectangular piece of metal on the mag follower. Easy does it. maybe 1/32 to 1/16 off. Don't know why it makes a diffrence, but on some mags it does. Have Fun!

Hey JacRyan

About those drums that don't fit and are therefore useless. I'll give you $100 for them.  [0:)]