Semi Thompson using AR-15 hammer, trigger, sear?

[reconbob]

I just sold an 80% receiver to a guy who is having a semi auto Thompson made

using the AR-15 trigger parts. He talked about it like it was old news and that lots of

people go this route. Has anyone seen one of these? Do they look good retaining the

original appearance? Do they work?

 

Bob

[anticus]

Yes to all. If you go to Weaponsguild.com there are several builds-all legal- of Thompsons on view from 80% and reweld receivers, using hammer style FCG w/AR parts and striker systems.

[reconbob]

OK, Thanks!

[anjong-ni]

According to Doug Richardson's writings, there are no "approved" methods of converting a F/A Thompson to semi-auto, and that the A-O Kahr semi-version couldn't pass muster today.

Some kind of rule that the weapon has to jam on the next round if the firing-pin sticks?

Can't wait to see what the investigators here find out. Phil

 

QUESTION : What is involved in making a semi-auto with my TSMG parts kit?

 

ANSWER : Unfortunately, to the best of my knowledge, as of this date (Jan. 2007) there is no ATF approved way of making a semi-auto gun from a TSMG parts kit as is done with a number of other machine gun parts kits. The assumption being that the semi-auto gun will have the outside dimensions of the original, look exactly like the original and use most of the original parts including magazines. Numrich Arms designed a semi-auto gun years ago that more or less resembles a Thompson. That gun is now manufactured by Kahr Arms. Neither of these companies has any connection to Col. Thompson’s Auto-Ordnance Corp. that invented, developed and manufactured the Thompson Submachine Gun. The N/K gun is not a true Thompson and not made to the original drawings. Therefore, very few Thompson parts fit it. Without an approved design to modify the TSMG to fire semi-automatically, the only option is to make an N/K gun out of a Thompson. Unless one is willing to spend a lot of money and register the gun as a short-barreled rifle, it is not a cost effective project. (My book, “Thompson New Production Semi-Autos” describes this process.) One is better off just buying the N/K gun. If a detachable buttstock is desired, the most cost effective way of achieving that is to fit one of my kits to the trigger housing. If it is desired to have a receiver that is as true to the original as possible, then one of my MS or 2S receivers can be used. But in the end, it still ends up as an N/K gun design, not a Thompson. I have a design for a proper semi-auto Thompson but no time to pursue it. I know others are working on their versions. Maybe something will come of it.

Edited July 25, 2016 by anjong-ni

[StooperZero]

it's an easy build too.

 

 

 

ATF approval means nothing unless you're producing revenue.

[Paladin601]

I have not heard anything and could not find anything on the Weapons Guild forum, that use's AR parts

 

 

But would be very interested to read about the subject

Edited July 25, 2016 by Paladin601

[Joe H]

Phil & Paladin,

 

Just as Anticus noted plenty of reading material here (both hammer fired (AR15) and striker fired):

 

http://www.weaponsguild.com/forum/index.php?board=105.0

 

You may have to join but its free.

 

Joe

[Merry Ploughboy]

IIRC, back when Timothy Polston developed his design for a semi-auto Thompson gun (see, for example, U.S. Patents No. 7,562,614 and 7,779,741) it was noted that there were alternatives to the Numrich and Polston designs that were apparently legal. Note that in the '741 patent, Mr. Polston discusses ATF considerations. I do not recall if any of the alternative designs were identified as using AR-15 components.

 

ETA: Beat by 1 minute!

Edited July 25, 2016 by Merry Ploughboy

[Black River Militaria CII]

With all due respect, this is completely wrong: "ATF approval means nothing unless you're producing revenue."

 

You are confusing ATF regulation of licensed "manufacturing" of firearms with building of semi-auto MGs by non-licensees that must be designed so as not to be readily convertible to FA function.

ATF has regulatory and enforcement authority over semi-auto MGs due to the legal requirement that any semi-auto must not be "readily convertible" to full-auto function or be assembled with any components that can be altered to fire full-auto. Years ago, when the semi-auto MG hobby was starting to grow, the attitude of many builders was that these guns had nothing to do with MGs and ATF had to authority over them Wrong! The semi-auto builders now understand that ATF has direct and enforceable authority to regulate how semi-auto MGs are built. Approval by ATF tech branch of a semi-auto design is essential to protect the builder and buyers from potential serious legal problems, liabilities.

There are older semi-auto MG designs that have approval letters from ATF, but which would now not be eligible for approval. I doubt that ATF will review these at any time and builders will continue to use the approved designs. I build a lot of semi-auto MGs and continue to abide by the older design requirements, but there are some designs that are still being built for which there is no provable letter of approval. The originators of these designs keep saying that they have a letter, but never produce it. This is not good.

The best procedure for getting an approval for a semi-auto MG design is to have an FFL07/SOTII build the first prototype for approval and register it as a post-May sample. Once submitted to ATF for approval, if it is deemed an MG, it can be returned for further development work since it is a registered post-May sample. A non-post-May sample wiil be confiscated.

Edited July 25, 2016 by Black River Militaria CII

[Paladin601]

Phil & Paladin,

 

Just as Anticus noted plenty of reading material here (both hammer fired (AR15) and striker fired):

 

http://www.weaponsguild.com/forum/index.php?board=105.0

 

You may have to join but its free.

 

Joe

Interesting, I guess I breezed over it to fast, did not see any mention of the AR parts. I saw the modified bolt and hammer design, and yours Joe. will have to read it again , i guess. thanks

[Joe H]

Paladin,

 

The sticky threads at the top started by sdk 1968 are all AR-15 hammer fired designs.

 

Joe

[StooperZero]

With all due respect, this is completely wrong: "ATF approval means nothing unless you're producing revenue."

 

 

Not in the sense you posted, Following the simple rules on anything us peons make IE: closed bolt, not readily convertible is good enough for the regular guy.

 

If you have a business or plan on mass producing a semi version of an MG you won't get far without an approval letter.