Is it a violation of the NFA?

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PocketRocket

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Is it a violation to have any M-16 part in an semi-auto AR-15?

Specifically, I was offered an M-16 bolt carrier for my parts-built AR-15 upper and I need to know if it would be illegal to use it. It would be the only M-16 part in the rifle.
 
No. Lots of people use bcg's that are rated for full auto. The bolt doesnt change the rifle to full auto. There may be some restriction if you are in cali or somewhere else with weird gun laws but I dont know anything about that.
 
TAKtical & Keaner - Thanks for the replies.

Keaner - special thanks for the link -- you can’t get more specific than that!
 
It's only a crime if the part in question is directly responsible for giving the weapon the ability to fire automatically and it is not a registered machine gun that is identified as being in your lawful possession. The only part of the M16 which allows for automatic fire is the trigger group, particularly the automatic sear. Apart from this, no other M16 part is any problem whatsoever.
 
It is my most earnest understanding that the only difference would be the metalurgy. An M-16 bcg would have to tolerate lot's more cycles in a given period of time, be able to reciprocate many many times is a short period of time, and do both while presumably being pretty darn hot. So metalurgy and perhaps a bit more metal here or there. I don't think, from a physical configuration standpoint...how the thing is shaped...there is a difference.

Presumably a cheap or middle of the road AR-15 bcg would work in a full-auto M-16 as well...but would fail rather quickly.
 
It is my most earnest understanding that the only difference would be the metalurgy. An M-16 bcg would have to tolerate lot's more cycles in a given period of time, be able to reciprocate many many times is a short period of time, and do both while presumably being pretty darn hot. So metalurgy and perhaps a bit more metal here or there. I don't think, from a physical configuration standpoint...how the thing is shaped...there is a difference.

Presumably a cheap or middle of the road AR-15 bcg would work in a full-auto M-16 as well...but would fail rather quickly.
HoosierQ: Incorrect. The M16 BCG has some slight differences:

carriers.jpg ar15carriers.jpg
 
Rail Driver - I now have the M-16 bolt carrier in my possession and I can readily see the differences that you displayed and I also know the purpose of the changes.

You also displayed the “AR enhanced” bcg. I was unaware of it’s existence until now and I would like to know what, if any, is the benefit from it. Thanks.
 
marginally slower cycling/lock time. Seems to be more reliable with heavier bullets (62gr+). a note - you probably won't see many SP1 style BCGs, and I have never personally seen a "half circle" style BCG - Most of the ones I've seen over the past few years have been the enhanced style. The enhanced style is definitely softer shooting in a gun with a carbine length gas system than the SP1 style BCG. I run a mid-length with an enhanced style BCG, but plan to upgrade to the F/A BCG as soon as I can divert some fun money.
 
An AR15 BCG will work in an M16, in semi auto only. The extra metal that an AR15 BCG does not have, it actually the sear trip. Without it, you cannot trip the sear for full auto function
 
Rail Driver - I installed the M-16 BCG then attached upper & lower together and it runs good.

I had a second AR-15 project going; this one is a AR-15 pistol. It is a new Bushmaster complete factory lower (circa 1999) and an 11” JT Distributors upper (supposedly made by FN -- barrel maker is unknown). I put a SP-1 BCG in it and it runs good. When I tried the M-16 BCG in it there was a jam after each firing caused by the case not being fully ejected.

Any insight as to why one works and the other doesn’t?
 
Rail Driver - I installed the M-16 BCG then attached upper & lower together and it runs good.

I had a second AR-15 project going; this one is a AR-15 pistol. It is a new Bushmaster complete factory lower (circa 1999) and an 11” JT Distributors upper (supposedly made by FN -- barrel maker is unknown). I put a SP-1 BCG in it and it runs good. When I tried the M-16 BCG in it there was a jam after each firing caused by the case not being fully ejected.

Any insight as to why one works and the other doesn’t?
As you can see from the photo, the M16 carrier is a bit longer. In your pistol, does the sere block extend above the sides of the lower receiver?
 
The extra metal that an AR15 BCG does not have, it actually the sear trip. Without it, you cannot trip the sear for full auto function

Unless you're running a lightning link (which requires milling on the bottom of an AR-15 BCG)

OP-

It's been pretty well addressed, but the M16 BCG in a title I AR is common and doesn't get ATF scrutiny at all. Now, if you have an M16 hammer, sear assembly and safety to go with it, you've got contructive possession (and especially if your receiver is milled for those parts to fit)
 
Rail Driver - Correction: my bolt carrier is the “half circle” type and not the SP1 as I had indicated.

I am not familiar with the term “sear block”. I looked up the Colt parts legend and it was not listed. Anyway, I opened up the receiver and the only thing above the walls of the lower receiver is the hammer and the captured hammer spring.

Can you straighten me out on this? Thanks…..Rocket

MachIVshooter - Since I don't know what a "lightning link" is and because the lower is a "stock" 1999 Bushmaster, I'm guessing I don't have it. However, I'm curious, so can you tell me about it? Thanks.....Rocket
 
Not all AR15's are equipped with a sere block. I wasn't sure if yours was or not.

To be honest I can't help much beyond what I've already done without detailed photos of the rig, or seeing it in person (doubt that's an option). Since your BCG is the half circle style, it's entirely possible that your lower receiver was designed for use only with that type of BCG, or that the buffer is too long, or that the buffer tube is too short. Either way, I would simply put the BCG that works in the pistol and leave it there, and put the one that works in the rifle and leave it there. There is no reason to switch back and forth.
 
Rail Driver - I appreciate that you took the time to help and for the education on all the bolt carrier types. Maybe the next time I’m in conversation about the AR-15/M-16 I might fool someone into thinking I actually know what I’m talking about! :D

“There is no reason to switch back and forth." I’ve been in places where one’s politics is met with deadly response. Having participated in war and riots in this country, I am not so naïve as to believe that it can’t happen here. So certain parts in certain guns could be appropriate given the right (unfortunate?) time and place. No slight intended.....Rocket
 
“There is no reason to switch back and forth." I’ve been in places where one’s politics is met with deadly response. Having participated in war and riots in this country, I am not so naïve as to believe that it can’t happen here. So certain parts in certain guns could be appropriate given the right (unfortunate?) time and place. No slight intended.....Rocket

Why would you need to switch carriers? If one of the two you have works in the pistol, but the other one doesn't, then you have no valid reason to put the non-working carrier in the pistol. I can understand wanting a backup BCG in case the one in the gun fails, but a backup that doesn't function in your firearm isn't really a backup is it?

I'm not saying there's no reason to switch from pistol to rifle and back - That's your choice and your preference - I'm assuming you only have one lower based on your comment - I wasn't implying there is no reason to switch from pistol to rifle - I was saying flat out that there's no reason to swap back and forth from one BCG to another in one gun unless one of the carriers breaks during use.

If you have two complete firearms (rifle and pistol) and both BCGs work in the rifle, but only one works in the pistol, then my advice is to stick to what works - If you want an upgrade, then it's time to do some research and find out what is compatible with your gun.

Politics, riots, war and self defense have nothing to do with what I said.

There is no appreciable benefit to switching from one BCG to another unless you're upgrading to a better one and are just keeping the old one as a backup - Swapping from one to another repeatedly is going to accelerate the wear on the receiver, the locking lugs and the bolt.

A non-working BCG serves no purpose at all in a gun unless you're intending to use it as a "decoy".

Perhaps there is a language barrier that caused my point to be unclear?
 
Rail Driver - Perhaps I was the one who was unclear. I have two lowers, both Bushmasters, one of which is a registered pistol lower.

My reasoning is that I want both to be capable of using a registered drop-in auto sear to legally convert them to full auto. That can’t be done unless both can use either a M-16 bolt carrier or carrier conversion block, so there is a reason for me. Does that make it more clear for you?......Rocket
 
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That does make it more clear. With the pistol, it's anyone's guess without detailed pictures or the gun physically in my hand where I can fire it, see how the function is, and find out where it's binding up.

Good luck.
 
You would also need to ensure that both models are low shelf to fit a DIAS, then the hard part is finding someone who will actually sell a registered one... Let alone the $12,000-$15,000 price tag
 
Unless you're running a lightning link (which requires milling on the bottom of an AR-15 BCG)
unless you have an SP1 carrier that it designed to work with.
 
I fire very hot loads in my target AR's. You really have to push the 600 yard loads. I use a Tubb weight in my bolt carrier and I use the heavy bolt carrier.

The Tubb weight and the heavy bolt carrier adds a tiny bit of delay time during unlock and they both add to reliability during bolt closure.

A high carrier mass to bolt ratio is good. The AK47 has a very high carrier mass to bolt ratio, so does the HK91 rifle.
 
Many DIAS's, both the unnumbered "legal" ones and the registered ones, are of very poor quallity, turned out in a hurry to make a fast buck. A very unhappy camper is the person who shells out big bucks (and perhaps takes a big chance in violating the law as well) only to find out that his DIAS is a piece of cast zinc junk that lasts only a dozen rounds.

Jim
 
Many DIAS's, both the unnumbered "legal" ones and the registered ones, are of very poor quallity, turned out in a hurry to make a fast buck. A very unhappy camper is the person who shells out big bucks (and perhaps takes a big chance in violating the law as well) only to find out that his DIAS is a piece of cast zinc junk that lasts only a dozen rounds.

Jim
... wouldn't an un-numbered DIAS be illegal? I've never heard of a legal machine gun without a serial. Possession of an unregistered machine gun (in this country anyway) is a federal crime, not just a chance of a violation.
 
If its not numbered, its not registered,ans not legal. If it doesnt have Form 4 paperwork, and cost in the range I mentioned before, stay away.
 
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