View Full Version : Full auto build, legal?

Tucker 1371
July 31, 2009, 01:40 PM
I was just browsing gunbroker today when I found a full auto lower receiver to a Sig 551 and it got me thinking. Would it be legal to buy the full auto lower and then finish the gun with parts from compatible semi autos?

I don't know and seriously doubt that The Sig 551 lower and 556 upper are compatible but if they were would this be legal? Don't full auto lowers or trigger groups have to go through the same processes as complete full autos?

July 31, 2009, 01:49 PM
That hasn't been legal since 1986, and even then you had to pay a $200 tax to do it.

Tucker 1371
July 31, 2009, 01:59 PM
So why is some guy on gunbroker selling a full auto lower receiver on gunbroker? Better yet why would anyone buy it?

July 31, 2009, 02:03 PM
It could be an already registered transferable full-auto lower, made before 1986....that is legal (in the free states anyways) but it's gonna cost some coin.

gun nut
July 31, 2009, 02:07 PM
Depending what part is registered with nfa could be used for repair with another registered gun. I'm not familiar with the gun your referring. Some have a registered sear, others maybe a registered receiver, some have a registered bolt, those are just some examples that come to mind. Hope that helps.

July 31, 2009, 02:09 PM
Got a link to it?...might help us out.

July 31, 2009, 03:37 PM
I believe that the SIG 551 lower is not the firearm; the serialled upper is*. Thus, I believe (I am not a lawyer!) that possessing a full-auto SIG lower is legal. However, if you also own a semi SIG 556 at the same time, you are in possession of a contraband machine gun, even if you never mate your SIG's upper with that lower—or, even that it would be possible to do so without some work. The BATFE can be very creative in these situations.

Best not to play with fire.


*The inverse of the AR-type rifles, where the lower is the firearm.

July 31, 2009, 03:40 PM
I searched gunbroker and found a couple of the auctions. I think that this is the one you are probably looking at.

Sig 551 full auto lower receiver 556 550 552 (http://www.gunbroker.com/Auction/ViewItem.asp?Item=135720655)

The sparse description and starting bid of only $1,300 is sending up more red flags than a Soviet May Day parade.

A legitimate full-auto lower receiver like that would probably have a starting bid of AT LEAST $10,000 and would already have several bids.

Tucker 1371
July 31, 2009, 04:40 PM
Sorry here's the link to the one I was talking about


and this one has me scratching my head too


Willie Lowman
July 31, 2009, 05:01 PM
The words "Post 86 sample" don't mean anything to you guys?

The second one that GSU posted is clearly torch cut. It is a parts kit.

Making a machinegun is still illegal.

Boone Hillbilly
August 1, 2009, 02:44 PM
Something for 02 SOT's to play with basically and then sale as a dealer sample or give demos:)

David Hineline
August 1, 2009, 07:56 PM
Fireworks are illegal, dynamite is illegal, yet every day people goto fireworks shows, and watch buildings destroyed with explosives.

Just because you don't have the permits for something does not mean other people don't.

August 1, 2009, 09:00 PM
Cut the OP some slack. He was just going with the odds. We've all seen some dumb things on GB, so dumb & illegal isn't that far a stretch, especially when it comes to MG parts.