View Full Version : Thompson question

August 13, 2009, 02:35 PM
Just went and got myself a thompson 1928 navy model in fairly good condition. But somethings been bothering me, when you look through the barrel about 2" from the chamber there is a ring ca 1/8" long. Never seen anything like it, almost looks like its there on purpouse, no visual marks on the outside of the barrel either.

Someone here have any experience about these things? Can it be dangerous to shoot?

James K
August 13, 2009, 02:58 PM
Well it shouldn't be there. It sounds like someone had a stuck bullet or some other obstruction and shot it out.

You can probably shoot it without any worry, but if you want to fix the problem, I think new barrels are available for that gun, both finned and unfinned, from Gun Parts Corp. (www.gunpartscorp.com).


August 14, 2009, 06:35 PM
Could it be a "gas check" ring that came off a bullet?:o

August 15, 2009, 06:20 AM
Thanks for the replies, will just go for it and test shoot it when i get some magazines.
A gunsmith i spoke with talked about that some guns have these chambers in the barrel to relive pressure or something, and it really does look like it was made with a cutting tool since it have such sharp edges. Will get it borescoped at opportunity.


August 15, 2009, 01:52 PM
Nothing I've found notes that the Thompson SMG had an annular ring in the chamber. Modification by a former owner, perhaps?

My money's still on it being a ring from overpressure obstruction - firing out a squib, as stated.

September 4, 2009, 11:11 AM
Mine doesn't have anything like that.:confused:

James K
September 7, 2009, 08:32 PM
One point I forgot to mention, and I apologize.

Most of the 1928's in the country started out as DEWAT's (DEactivated WAr Trophy) under a program by the (the) Alcohol and Tobacco Tax Unit of the IRS. Any GI or anyone else owning an unregistered souvenir auto weapon could have it welded up and keep it. Importers, sitting on tons of auto weapons overseas, promptly brought guns in by the ton (STEN's, M3 SMG's, and various models of the Thompson were most common). The guns were deactivated by dropping a steel flat head bolt into the rear of the barrel and welding around it, then welding the barrel to the receiver. The guns then became "non-guns" and were sold without any paperwork at all.

Human nature being what it is, a lot of those guns were "REWATTED" (restored to firing condition). This was usually done in home workshops, since it was illegal, and some barrels were damaged by attempts to drill out or otherwise remove the chamber block. Later, a magazine writer made a big scandal about the program and it was stopped. GCA '68 required registration, during the amnesty, of all DEWATs, either as serviceable (opened up) or unserviceable (still welded). Anyone today possessing a registered welded gun can restore it to firing condition by payment of the $200 tax, since it is already registered.

I think removing the chamber block is the explanation for the ring in your barrel, not a shot-out obstruction. Sorry for the light not dawning sooner. If the barrel is welded to the receiver by a small tack weld, it would confirm that the gun had been a DEWAT.