MGC THOMPSON BOLT

Hey there fellas! I'm new on the forum, I registered because I own a MGC 1921 Thompson that is giving me a lotta trouble... The bolt face is completely smashed and worn out. I've looked everywhere and came up with nothing, I've asked Francky (I think most people on this forum know him) and he hasn't been able to help me either...I've tried gunbroker, but I couldn't register because I don't live in the US (Im from Spain)...I've been browsing the posts and seen some people have been able to get metal bolts made (or new mgc zinc bolts)... Can any of you help me get a new bolt for my Thompson? If not, please can you tell me where to look for one? I've already pmed a couple of members:-) but I just thought it would be better to open a help thread... I'm desperate, I don't want to throw away my gun just because of a broken part... Thank you so much for your help and time!

Hello mickey, welcome to the forum

I'm sure there'll be one or two members here that might be able to sell you a spare bolt. If you have the opportunity to buy two, and you fire your Thompson regularly, buy them as the standard zinc alloy bolts do wear out

One thing to check is which type or version of MGC's 1921 you have. Early and late models fired different cartridges and the Extractor differs between them.
A photo of the Bolt showing the extractor type you need would be very useful.

A good source of MGC Thompson spares right now is John at www.plugfirecapgunsuk.com
He might be able to help you too.

Hey Cerwyn! Thanks a million for your help! From what I've seen in other posts mine is one of the early models... I'll post a pic of the bolt when I get my hands on a camera... I'll get in touch with John, I bought some stuff from him in the past. :-) please if any member has spare bolts for sale (metal or zinc) let me know. Thanks guys!

It's a pleasure

One thing to consider... if your Thompson is an early one, it is possible to convert it to fire the later c.p. cartridges. You'll need a bolt, Detonator Chamber, a little work in the receiver to allow room for the later bolt to move freely, and of coure new cartridges.

The c.p. cartridges are an improved design, fire well, are reasonably plentiful to buy new so an upgrade could be worth considering.

Have a good read through the MGC Thompson category, there'll be photos of different bolts, extractors, plus details on conversion should you need them.

Thanks for your help cerwyn. Will upload some pics when i find some time just to make sure what model i have... I'll open a new thread on the "for sale" section:-) if it really is an one of the early models I'll consider doing what you told me... Thanks again!

Here's some information that should help you... The photos shown in this article are of the late type Zinc Bolt and c.p. Cartridge:

Here are some pics... so, I guess I was wrong and this is one of the late models am I right? I want to thank everybody who has helped me and those who have taken the time to read my posts... I may be able to get a zinc bolt, but I'm still looking for a steel one...

Do any know who is selling 7mm pfc cap primers in the U.S?
Also is there a substitute that can be used for cap primers?

1. I have an early model MGC Thompson with the bolts holding the receiver on top with a long flat metal bar running down the length of the barrel, is this considered open barrel?
2. Also I bought a dentonor for the chamber that fits, with the pfc shells ( but no caps which are hard to find).
3.when I chamber the shell it does not go all the way in. Is
this how it suppose to chamber or does the shell suppose to chamber flush?

If I were to change to a steel bolt, then change the barrel to a 45 acp blank firing barrel, will I be able to fire 45 acp blank rounds in my mgc without damaging my receiver?

If I were to change to a steel bolt, and change my barrel to a 45 acp blank firing barrel, could I fire 45 acp blanks in my mgc Thompson without damaging the receiver?

Hi and welcome to the forum!

The MGC Thompson is a popular model for sure. Many collections started with this exact same model. It is very durable, with the exception of the bolt itself.

You've asked a few questions, so I'll try to help out a bit........

1.It does sound like you have an open barrel model, which puts its manufacture prior to 1979 I think it is. Those are my favorites as you can get smoke to vigorously vent from the muzzle when firing it.
2. If you bought an original chamber, it will fit the receiver, but the detonator pin will need to be custom made to work with the newer style cartridges that take the 7mm plastic cap. When the open barrel models were originally made, a different style cartridge was used and required a paper cap, which is no longer made.
3.The MGC model upper receiver is a one piece cast design and that includes the barrel. You cannot change barrels. Please do not attempt to fire any type of actual blank cartridge as the metal used to construct these guns will 100% not take the stress created by blanks.

Take a look around here on the forum and you'll find some great info and some very great and helpful members!

If you have questions, ask away!

JL

I sent 2 photos of my mgc Thompson, I put in a detonator in the chamber that actually fit but when I chamberd a pfc shell it seem like the shell only midway, is this how it suppose look or does it goes in flush with the chamber?

Do anyone know where I can purchase 7mm plug fire caps in the U.S?

The bolt depth looks good to me. You need to get the detpin length as short as possible without the bolt hitting the receiver.

If you strip the gun down and put the bolt back in the upper receiver as you can see the gap between the bolt and receiver better.
Then place a non loaded cart (primer and piston only) in the chamber and you should still have a couple of mm between the front of the bolt body and the receiver (just behind the mag).

I hope this helps

Yep..........what 8Ace said.........judging by the pics you provided, you should have a lot of bolt-to-receiver clearance so if you wanted to shorten that detonator pin you could.
The firing design of the MGC Tommy doesn't really require that the bolt go into "battery".

Occasionally you can find a replacement bolt up for sale on ebay. The same can be said for finding caps - just not very often for sure.

Where do you live in the US?

Yes I live in the U.S and I can't find 7mm caps on line out here, they are all over seas.

I have stripped the gun down to check the distance of the bolt ,detonator and chamber. But you maybe right about shortening the pin, cause even with no 7mm caps in the shell it still sticks out the chamber a lil bit. So what is the best way to shorten the pin without damaging it?

If you have a period-correct chamber, the custom pin can be removed and easily ground down with a disk sander, etc.

Ok

If I don't have any size 7 mm caps for my MGC Thompson, what else could be a substitute ?

I do not know of any substitute for the caps. Sorry.

Have anyone tried to use regular shell primers in place of 7mm caps?
And if so, did it or would it work?

Which is louder 7 mm Or paper caps