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80% Receiver Wants To Know


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I checked the Thompson FAQ and I don't see the answer to my question there. Being entirely new to this business, I would like to know the issues involved in machining an " 80% receiver" to semi-auto capability. From what I can gather, this requires a semi-auto trigger group as the full auto set-up as found in the parts kit will not work. That being the case, it appears quite impractical to even consider doing this as one might as well go out and buy a semi AO or Kahr and forget the headaches involved in machining. Considering all the FA parts kits out there, and the demand for 80% receivers, some knowledgeable person might want to address this in the FAQ 'cause I'm sure there are a bunch of guys out there who think that one day, they're going to just going to take that 80 percenter and hog it out to semi-auto capability without a problem.
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The 80% 28/21 receiver can't be milled out to 27A1 specs due to the fact that the 27A1 receiver is 1/10 inch shorter than a 21/28 receiver.

 

I would not advise that any individual try to make an 80% 21/28 receiver into any functioning firearm- not even semi-automatic.

 

There are 80% 27A1 receivers that out there that can completed into a semi-auto Thompson. I have Richardson 27A1 that has been completed into a functioning semi-auto receiver.

 

Just my $.02 worth.

 

Norm

 

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Easiest legal way to actually build one of these bad boys to fire is to make a SINGLE SHOT firearm. Order your 80% reciever without the mag slot milled in at all, and you can legally use the open bolt. AJ machine will do this for you. If you remove the butt stock and permanently alter your lower so you can never install it again, you can even keep the short barrel. (it will be a pistol, then) Otherwise, you have to register it as a short barreled rifle. Or install a 16 inch barrel and use the butt stock.
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QUOTE (dpcd67 @ Jun 12 2006, 09:19 PM)
Easiest legal way to actually build one of these bad boys to fire is to make a SINGLE SHOT firearm. Order your 80% reciever without the mag slot milled in at all, and you can legally use the open bolt. AJ machine will do this for you. If you remove the butt stock and permanently alter your lower so you can never install it again, you can even keep the short barrel. (it will be a pistol, then) Otherwise, you have to register it as a short barreled rifle. Or install a 16 inch barrel and use the butt stock.

WTF?? http://www.machinegunbooks.com/forums/invboard1_1_2/upload/html/emoticons/ph34r.gif

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http://www.machinegunbooks.com/forums/invboard1_1_2/upload/html/emoticons/banghead.gif
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QUOTE (PhilOhio @ Jun 13 2006, 06:43 PM)
QUOTE (Ron Mills @ Jun 13 2006, 06:27 PM)
http://www.machinegunbooks.com/forums/invboard1_1_2/upload/html/emoticons/cop.gif

??? http://www.machinegunbooks.com/forums/invboard1_1_2/upload/html/emoticons/blink.gif

 

Basically three of us have said with one icon, what took you 378 words... http://www.machinegunbooks.com/forums/invboard1_1_2/upload/html/emoticons/blink.gif

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My post wasn't aimed at you, Phil; the icons are fun...I put mine there so maybe the guy doesn't:

a) blow something or himself up, and/or

http://www.machinegunbooks.com/forums/invboard1_1_2/upload/html/emoticons/cool.gif waste time, machinery, etc.

Ah, waddu I know. I can't put the http://www.machinegunbooks.com/forums/invboard1_1_2/upload/html/emoticons/woot.gif guy on every post!

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Aside from the legalities, I have never seen 80% Thompson receiver that did not have the "magazine well" not completed.
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QUOTE (Norm @ Jun 13 2006, 09:39 PM)
Aside from the legalities, I have never seen 80% Thompson receiver that did not have the "magazine well" not completed.

Not a very good first post I would say.... Maybe the next one will be better informed.... I'm hoping the single shot open bolt part was done tongue in cheek.....

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Phil,

 

Have you ever seen the SWD (Cobray) 12 Gauge open-bolt shot gun? http://www.machinegunbooks.com/forums/invboard1_1_2/upload/html/emoticons/ohmy.gif

 

I don't know about shooting this thing. The stock looks unforgiving! http://www.machinegunbooks.com/forums/invboard1_1_2/upload/html/emoticons/sad.gif

 

I found this photo at UZItalk.

 

http://i6.photobucket.com/albums/y204/mbsennett1/openbolt12.jpg

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Phil,

 

Me-thinks it is NFA because of barrel length or even over-all lenght. The barrel looks shorter than 18 inches and I think the over-all lenght of a shotgun has to be 26 inches.

 

Shooting my SBS is scary enough as it is and it is a "break breach" gun. I would be hesitant to fire a "slam fire" 12 gauge. http://www.machinegunbooks.com/forums/invboard1_1_2/upload/html/emoticons/dry.gif

 

Norm

 

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Hmmmm. It appears there is a LOT of false advertising going on with these 80% receivers. I have seen more than one advertisement for them stating they could be built into functioning semi-auto receivers. Since they can't be built into full auto subguns, OR semi-auto receivers, that makes them a VERY expensive dummy receiver, or a very expensive paperweight. http://www.machinegunbooks.com/forums/invboard1_1_2/upload/html/emoticons/laugh.gif

 

Dep

 

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One of the most significant features of an "80% receiver" is that it is a "non-firearm" when

you buy it. Because it is a non-firearm and non-machine gun, it can LEGALLY be finished into

a semi-auto. This may sound trite, but you cannot reweld pieces of original Thompsons together

to make a semi-auto - the feds won't allow that.

Many 80% machined receivers have been successfully finished into a variety of legal working

firearms, and the mechanical aspects of these is limited only by the ingenuity and imagination

of the designer and hobbyist. Some have even made guns in different calibers.

If your definition of a semi-auto is something you can make with an 80% receiver, an

original parts set, and a file and a screwdriver, and do it at the kitchen table in an afternoon,

well then yes, no one has come up with that one yet.

But many have used any number of "transplanted" gun mechanisms to achieve semi-auto,

from M-1 Carbines, Garands, Ithaca M37, Remington M870, and even made their own action

parts. So far the people that do this are hobbyists that do it for themselves, in private, and

not for resale. These projects would not have been possible without a legal non-machine gun

receiver to build on.

So, its not really right or fair to say it can't be done and that the sellers of 80% receivers

(regardless of who they are) are misleading their customers or participating in "false

advertising".

A quality 80% receiver is a real advantage to the hobby builder because the builder does

not have to buy a raw bar of steel and spend big bucks on the tooling and fixturing to do the

tricky stuff (how'd you like to machine a double angle ejection port or a double compound

angle feed ramp?) and can instead concentrate of the bolt pocket and semi-auto mechanism.

 

Bob Bower/Philly O

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Reconbob,

 

When you say 80% receiver I assume you are speaking of an 80% 21/28 receiver.

 

When looking into "building" a gun to put my registered conversion pin in, I contacted the ATF and (basically) asked them if this registered conversion pin could be put into 21/28 80% receiver if it were completed to semi-auto specs; that is, being finished to only house a 27A1 bolt and not 21/28 bolt.

 

The ATF told me "No." They said this would definitely cross the line on having "machinegun receiver" being to close being completed. This info was given to me verbally, and not in writing.

 

This is why I got a 80% 27A1 receiver from Doug Richardson and had it completed as my host gun.

 

Now before everyone beats me to death with "get it in writing" or "the word of just an agent is highly subject to be incorrect," let me ask one question....

 

If people can buy an 80% 21/28 receiver and legally make a semi-auto gun, then why doesn't anyone make a semi-auto receiver that is the same size as 21/28? http://www.machinegunbooks.com/forums/invboard1_1_2/upload/html/emoticons/huh.gif

 

The demand has been stated for such a gun and it would solve many problems with semi-auto modified mags and trigger frames that have to be modified to fit a semi-auto gun. Also, the tooling seems to be in place to make these for sale.

 

Respectfully- Norm

 

If there is something I am missing, then please educate me. http://www.machinegunbooks.com/forums/invboard1_1_2/upload/html/emoticons/wink.gif

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QUOTE
The demand has been stated for such a gun and it would solve many problems with semi-auto modified mags and trigger frames that have to be modified to fit a semi-auto gun. Also, the tooling seems to be in place to make these for sale.

 

I think the answer to that is BATFE. As in getting the semi-auto design approved by the feds before being able to sell the receiver.

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Norm...

I don't know what a "registered conversion pin" is, so I cannot

address that issue.

Why hasn't anyone made a semi-auto closer to "original" than the

WH/Kahr design? I don't know. I do not think it will be too long before

one or more designs are available. Designing and putting a gun into

production - even on a small "designer" scale is a significant, expensive

undertaking. A big name gun manufacturer puts hundreds of thousands

of dollars (if not millions) and a cadre of engineers, designers, and

machinists just to get to a production sample stage. Nobody is throwing

that kind of money and resources at a semi Thompson, but there are

inventors out there working with limited resources and they are getting

real close.

 

Bob

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Bob,

 

The registered firing pin is a device that converts a 27A1 into a full auto gun. It is firing pin that remains fixed in place instead of floating in the bolt. It basically turns a 27A1 into an open-bolt gun. After this is put in, simply remove the disconector and presto....full-auto 27A1.

 

There were about ten of them registered before the '86 ban by Broadhead Armory.

 

As for finishing a 21/28 size display receiver into functioning semi-auto, I'll pass. That's just a little closer to the line than I would like to get. This is why I asked the ATF before trying to have one built.

 

Maybe someone out there has an answer to this question in writing from the ATF in a response letter.

 

Norm

 

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I do find it interesting that the companies that make those 80% receivers and claim they can be finished into semi autos do NOT post any letters or documentation from the ATF stating they have been approved for manufacture that way. Seems like that approval should have been received BEFORE they started making that claim. http://www.machinegunbooks.com/forums/invboard1_1_2/upload/html/emoticons/blink.gif

 

Dep

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