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thompson semi from kit

5506 Views 21 Replies 11 Participants Last post by  Tom Kelly
can anybody tell me where to find info on building a semi 1928a1 thompson from a parts kit?
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Someone in the current SGN is advertising an 80% Thompson receiver but I don't know if it is semi or FA.
We have compared the parts from a semi kahr arms tommy and the 1928 lower reciever will fit. If you bought the semi receiver, bolt group and trigger group, you should be able to make a nice semi auto. You will have to loose the shoulder stock however, as it will make it a short barreled rifle, nfa weapon. The 80% recievers can be made either way full or semi

Hey every bit of info out there on this subject points to the fact that they say just buying a new or used semi thompson is cheaper than all the changes that would be necessary in order for the BATF to consider it to be no longer a FA gun... Thats why you won't find much info on it. I have seen a guy that takes a semi auto 28 style model that is being produced to day that puts the Auto/Semi selector back in and makes it hold the bolt open for quick drum changes which is an awesome idea no more third hand tool...

You have four factors you would have to deal with in order to make it semi only.

1. Closed bolt operating only
2. Modifying it enough so FA parts could not be installed as in the 1919a4
3. The cost of the parts that you would be modifying are costly for an experiment
4. To SBR or not to SBR

All these things could be done but its the cost involved in doing them. How would you feel about cutting on an original trigger frame? One alternative would be sarco's cut trigger frames I think they only have them for M1A1's though. 80% receivers are available from www.philaord.com. T&S manufacturing can put original markings and make a lot more of the surfaces more correct, but by the time your through you may be able to buy two or three new Kahr thompsons... It's all about what its worth to you and how far you want to take it... I for one would love to see some of the WWII thompsons back in action with maybe an ar15 trigger and sear setup could be possible they did it with the sten and some other sub guns...

This is a good thread lets keep it alive... Lets see if we can get some of those old sub guns back to the firing line...
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It is a heartbreaker, but almost impossible to build a legal Thompson. By the time you replace/modify the parts to make it legal, you have no original parts.

The 16 inch barrel on a thompson looks goofy.

I do military vehicle restoration and reenactment from time to time, and will tell you that if you want a functioning Thompson like gun, buy a Commando Arms. They are cheap and function much closer to the original. I even have an early Commando arms open bolt gun. These use the old Grease gun bolt and magazines, and the original Thompson stock. At least most of the parts are more original than any Thompson clone.

Just my two cents worth. I'll post some pics later.
I've had some thoughts on getting an M3 grease gun converted to semi. If I can work out a few things, then all those IMA grease gun kits they sold could have a new life. I've worked out the FA bolt blocking and closed bolt problems. now I just have to work out the trigger problems. If I can get it all to work, It'll work for an MP40 as well. Happy happy joy joy.

Yeah I was tempted to buy one of those grease gun kits but never did. Nothing like adding another GM product to the gun vault
Why does having a 1928 quick release stock make it a NFA weapon? Will the overall length not be long enough even with a 16" barrel? I think its only got to be 26" long right to be considered a rifle? The barrel is 16.5 or more with the cutts.

What am I missing?

Check out this site. Got some pretty good stuff:
Thats a

Thats a cool place to pic up links from they have a nice pic to compare a FA bolt too to see alot of the areas you would have to make mods...

They also had the www.tommygunner.com web link there he is the one that will install that switch so you don't need the third hand tool to install your drums...
Kali Komrade said:
They also had the www.tommygunner.com web link there he is the one that will install that switch so you don't need the third hand tool to install your drums...
Yeah for $335.00. For that I will use the third hand...

I like there site but man they are really expensive!

You would spend twice the cost of the semi gun just to get it looking like the FA using there services.
Hey I

Hey I agree but some people have money to burn as I stated up further in the thread by the time you try to build a kit into a semi kit you could by 3 kahr thompsons by the time your through... But all said in done if I had a 28 model in semi I would spend it to not have to use the third hand device, but thats just me... Your dead on they are very expensive...
Yeah its a real shame.

They really need to offer some package deals so somone like me who has one of these $800 guns can spend about $400 more and have it really look nice!

I have mine back at Kahr arms, hopefully being fixed for the last time, but I plan to do a lot with it.

I want to do the SBR, Lyman rear sights, removable rear stock and probably a closer cocking knob, org style selectors with hold open if priced right and mag release replacement. Basically what the guy did on that first site.

So... whats been wrong with your thompson IMBLITZVT and is it a Kahr or pre Kahr unit your having problems with... See I was thinking about ordering a Kahr unit for my outta state collection but if they are not that good I search for a pre Kahr unit... That kinda sucks if your having problems with something that has been reproduced so many times it should have all the bugs worked out of it.
I can't imagine trying to build a Thompson from whats available. Thats why I didn't jump on the kits when SG had them for $529. I've thought about it, and there is too much for me to re-engineer without knowing anything about Thompsons. I did finish a build recently that a Thompson fan may like. I took it out to the range today and I think I have worked the last of the bugs out of it. Check out my Soumi M31. http://s98.photobucket.com/albums/l273/acmech/

If you choose to build a Thompson, keep us updated on your progress.

Nice where did you get the longer Barrel AC... How well does it empty out??? I may have a few question on that one for you...
Kali Komrade said:
Nice where did you get the longer Barrel AC... How well does it empty out??? I may have a few question on that one for you...
The barrel is .749 inches in dia. I cut about 5/8 inch of the end of the barrel down, and then with a piece of 3/4 inch 4130 chrome moly from aircraftspruce and speciality, part no. 03-04900 I bored the 3.5 inch piece out to match with about .001 press fit and tapped them together. then I tig welded it at the seam, and I had a 16 inch barrel when I was done. I put the barrel back in the lathe and cut the total length down to 16.25 inches. I am also using the already ATF approved barrel takedown feature as well, and thats pretty cool I think.

There is a LOT of info in the specific build forum on weaponeer.net. I got a lot of ideas from the guys there, and added to some of them. Some of the last posts are here.

I think I am the first to complete a semi so I've made a lot of mistakes others won't have to. One thing I figured out today is the trunnion that is pressed into the receiver will eventually work its way out. Kinda messed up my range day, but I was happy to be able to get two drums full down range. My next trip will go a lot smoother. I posted on it at weaponeer, and I posted my fix. Feel free to ask any questions, this was a hard build, but I'm happy I'm done. My next one will go much quicker.
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bolt hold open

All Thompsons I've seen have a bolt hold open built in, see pick at link, just raise
while holding bolt back. this will lock bolt to the rear.

1928 A1 semi Thompson/ 80 % reciever !!

I withdrew this posting because of an impending court case of myself VS the 80% Thompson receiver builder I am out over $3000.00 Don't do the same thing I did!!

Okay... So who is this up in Wisconson maybe I'll have to google this one to figure it out... Are they on the web OTI?

I was looking at www.philaord.com anyone delt with them yet?
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