AR: Semi vs. Full Auto BCG?

[varob]

After researching spare parts for my AR, I see that you can buy Semi or Full Auto bolt carrier groups.

I searched some of the AR sites to see if one was better quality than the other and soon discovered there is a debate on whether buying a full auto BCG was a red flag for the BATF?

Some say a FA BCG is a full auto part, therefore an attempt to make your semi, full auto.

Others debate that full auto is in the fire control, therefore the BCG has nothing to do with it.

1. What do you all think?
2. What other spare parts should I keep on hand for my AR?

I'm looking forward to reading your opinions on the subject.

[DefensiveCarry.com]

[MattInFla]

It is, apparently, legal to have an M-16 Bolt Carrier in a semi-auto. See the ATF letter toward the bottom of this page: BATF NFA Hand Book Concerning M16 parts Used in an AR15. - Semiauto Rifles

However, the ATF handbook specifically mentions that having an M-16 Bolt Carrier in a semi-auto rifle is a no-go.

So it seems there is conflict, and someone might end up being a test case. It won't be me....

As for spare parts, a number of manufacturers offer field repair kits with replacement springs, pins, screws and those pesky detent points (which I magically manage to lose on occasion), along with the trigger, disconnector and hammer.

Matt

[The Cat]

On page 125 of Gunsmithing The AR-15, Patrick Sweeney writes:

As the carrier is the least important full-auto part, and it does have some use in semi-auto rifles, the BATFE has been unconcerned about M-16 carriers. However, "unconcerned" and "approving use" are different things.

Me, personally, I wouldn't want the minimal effect the extra metal at the back of the carrier would have on cycling to land me in a legal gray area.

The one thing I DO like about M16 carriers is the shrouded firing pin tunnel... but lots of regular AR carriers have that feature nowadays... so with these two things in mind I wouldn't even bother with an M16 carrier.


+1 on what Matt says about spare parts :)

[nlax2011]

Agree with the above. Go grab a copy of that letter. Certainly not forbidden, plus there are several AR that come with a "full auto" BCG.

Only reason for someone to be a test case is if your AR somehow went into FA.

[Chuck R.]

Agree with the above. Go grab a copy of that letter. Certainly not forbidden, plus there are several AR that come with a "full auto" BCG.

Only reason for someone to be a test case is if your AR somehow went into FA.

Agreed, my Colt LE6920 came with a M16 bolt carrier from the factory.

Here's a quote from the AR15 "Chart" that explains why they feel an M16 carrier is preferred:

The M16 bolt carrier serves two functions. The first is that the firing pin is fully shrouded so that the hammer is cocked by the carrier and not the firing pin itself. The second is that the M16 bold carrier is heavier and therefore increases "lock time" (or the amount of time that the empty case remains in the chamber after the primer is struck by the firing pin) which aids in extraction. The heavier carrier also reduces the felt recoil impulse which in turn reduces wear and tear on the other internal parts of the carbine.

M4 CHART

Chuck

[KevinDooley]

FA BCG in a semi gun is a complete non-issue as far as the BATFE is concerned - the above letter and the fact that nearly every high-end AR maker (including the usually gun-shy Colt) should be considered a clue.

The biggest reason I would see the need for one would be the what was quoted from the chart in Chuck's post. In addition to that I would add that since most commercially available rifles (especially those that come with semi carriers) are over-gassed and could actually benefit from the extra mass of the FA carrier. Also, every FA carrier I've seen has had a properly staked gas key - I can't say the same about the semi-auto carriers I've seen.

As for spare parts, if you have an extra BCG it wouldn't hurt, but really the part that will break out of it that you'll need would be the bolt. Many VFG and after-market pistol grips for the AR will allow you to store the bolt in it. That's what I keep on hand for a spare.

[mcp1810]

I got one for the H-BAR match I built. I have an older Bushy carbine that I am debating switching to a heavier carrier or just going with the H2 buffer.

As far as spare parts, you can't have too many firing pin retaining pins. Or as the drill sergeant refered to them "Oh $%^& pins!" Try dropping one in some pine needles some evening and you will instantly know the origins of that name.

[msgt/ret]

Being fairly new to AR rifles myself could someone explain or provide a link to pictures showing the differences between an AR-15 and an M-16 BCG.

[Ring]

non issue.....

[KevinDooley]

Being fairly new to AR rifles myself could someone explain or provide a link to pictures showing the differences between an AR-15 and an M-16 BCG.

There's several pics in the first few posts that show the differences here:

AR15 V. M16 Bolt Carrier - M4Carbine.net Forums

[msgt/ret]

There's several pics in the first few posts that show the differences here:

AR15 V. M16 Bolt Carrier - M4Carbine.net Forums

Great link, from the pics it is easy to tell them apart.

[Sarge45]

Colt and Bravo Company (BCM) sell their guns with full auto BCG's. Must not be a problem. I own both guns and have the proof.

[HuttoAg96]

Noveske, Spikes, Daniel Defense... all the top tier or semi top tier (Spikes) ARs have an auto/M16 BCG

[The Cat]

Colt and Bravo Company (BCM) sell their guns with full auto BCG's. Must not be a problem. I own both guns and have the proof.

Yeah - I agree. My mind's changed - if COLT will send them out, they must not be a problem :)