Will a full circle bolt work in an ar15 or is it intended for an m16.  I just bought a new military issue m4 barrel from a guy and he is giving me a "full circle bolt" with it.  All of my present bolts seem to be the half circle variety.  I was just wondering if I can use the one he is sending or even if I am allowed to possess it without owning an m16.  maybe I should pitch it at the post office before i get home.

It sounds like you're talking about the bolt carrier.  The FA M16 uses the "full circle" bolt carrier, where the bottom-rear of the bolt carrier trips the sear.  It's not needed on the semi, so the semi BC will work.

IIRC, it's considered part of a FA gun.  Maybe someone can attest to the legality/illegality of this BC in a semi rifle, even in the absence of a FA trigger group or posessed components.

it depends on how far forward the lower half of the "circle" goes.

If it is far enough forward to trip a FA sear, it is an M-16 part, and therefore an NFA part.

I could be wrong though- there are many more knowledgeable AR people here than me.

Semi AR15 bolt carrier have been made in boith the full and the half circle style.  the full auto bolt carrier have a full circle but the bottom section is about two inches in length.  if you look at it, the bottom section of the circle will extend pass the upper receiver takedown pin lug.  the semi full circle usually will end right at the edge of the takedown pin lug and it will not extend pass the lug while fully seated in the receiver.

SJ is correct, if you put a full auto bolt carrier in your AR, it is consider a machinegun part, you can get into big trouble.

Hope this helps.

I think from the descriptions that it might be full auto.  Can anyone tell from these pics?

www.angelfire.com/pa5/fq1234/carrier1.jpg

www.angelfire.com/pa5/fq1234/carrier2.jpg


http://www.angelfire.com/pa5/fq1234/barrelandcarrier.jpg

Edited to say:

I can't seem to get the links to work.  If anyone is interested in helping me email me at [email protected] and I will send the pictures.

That is the right angle to take the picture of the bolt carrier, you have to shoot the shot with the bottom of the carrier facing the camera.  but from the first picture, i think you got yourself a full auto carrier there.

Some say illegal,some say legal,I go with the legal,as long as it does not fire FA with the parts installed. Hope this helps.www.ar15.com/forums/topic.html?b=1&f=6&t=147440

Yes, I think it is most definately a full auto carrier.  Thanks for the link also, very interesting thread.

Zoomer, how could you, in good concience, send anyone to that hell-hole of a thread?  But it was good reading...
My opinion based on fact:
The carrier, while being an M16 part, is not illegal in your AR15.  It cannot make the gun function in FA, like an Auto-Sear, and it is not even part of the fire control group.
The reference to Bushmaster in that other thread was kind of amusing, since Bushmaster is fast to point out that they will sell you the RIGHT parts ASAP.
Bushmaster is in the business of sales.  I have seen [private] letters from ATF on this topic and they strongly RECOMMEND that you don't possess M16 parts.  That does not make it law, that merely is them letting you know that the presence of such parts can lead you down a bad path though ignorance or appearance.
This advice is usually given to those who already posses an MG and want to know the legaities of mixing & matching parts: uppers, lowers, etc.
The ONLY registered part is the sear, and they don't make any new ones for civilian use, so you better find one WITH papers.

Royce, you may or may not be mistaken about your opinion based on fact. However, which one of us wants to be the one to go through the hassle of finding out? I'd get a new carrier, or have that one milled to AR specs, and never, ever, have to worry about it ever again.

Royce, you may want to slow down and look at cause and effect.

Back when the AR-15 was first offered, some people figured out that if you load soft pistol primers into your 223 cases, you could get the rifle to slam fire by hammer follow down.

This method required that you change out the fire control group, without adding the auto sear to allow the selector to take the disconnector out of play on full auto setting.
Since at the time, only adding the sear was the evil, the rifles were not machine guns.  The BATF changed the laws regarding the AR-15's to read that insertion of any M-16 FCG would constitute the intent of creating a machine gun.  

This is the reason that you can not install "any" of the M-16 FCG parts in the AR-15 rifle, including just the carrier.

DANO523

Can you provide the code section stating where the insertion of any M16 parts makes the rifle a machine gun?

Before this goes any further, read www.ar15.com/forums/topic.html?b=1&f=6&t=147440&w=myTopicPop, 'cause this has already been hashed out by the pros.  You CAN have an M16 bolt carrier in yer AR.  The distinction lies in whether or not the addition of M16 parts makes your AR fire full auto.  The above thread is long, but well worth the read.

Send Kurt at KKF in the Industry section your bolt carrier and he will millit to semi specs and mail it back to you for $30.  I have my full auto Colt carrier there right now getting modified.

Zoomer, how could you, in good concience, send anyone to that hell-hole of a thread? But it was good reading...

Because I think it answers fq1234 question.  I did not say it was a good idea. I said it is not illegal(IMHO).  

My opinion based on fact: The carrier, while being an M16 part, is not illegal in your AR15. It cannot make the gun function in FA, like an Auto-Sear, and it is not even part of the fire control group.

 I agree,as stated in the thread.

The ONLY registered part is the sear, and they don't make any new ones for civilian use, so you better find one WITH papers.

 There are two different types of "sears".Drop in auto sears (with papers) and Full auto sears (for drilled receivers),however,fq1234 question was "I was just wondering if I can use the one he is sending or even if I am allowed to possess it without owning an m16."  My answer is yes,you could use it. Sears of any type are a whole different ballgame,but he did'nt ask that.  ps. I am not a lawyer but I think you get a more informed answer in the "Legal Forum".