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View Full Version : AR15 vs M16 BCG I need the 411


Super Spy
07-06-2009, 12:22 PM
Please explain the difference between a BCG (Bolt Carrier Group) for an AR-15 and an M-16. Are they interchangeable? Are there legal concerns in Cali? Aside from selective fire, does the M-16 BCG have any other advantages?

I'm curious and know I'll get plenty of feedback here, and I want to buy a backup BCG in case I have a break. Do I need to check headspace or anything when using a different BCG? Any suggestion such as buy this or stay away from that?

Thanks for your feedback in advance!

Richie Caketown
07-06-2009, 12:27 PM
i think your thinking of the semi auto vs full auto BCG right? The full auto BCG has more meat on it . As far as the benefits i am not truely sure . As far as a back up BCG i think you should just keep an extractor/firing pin as back ups instead of an entire BCG

cryptkeeper
07-06-2009, 12:28 PM
M-16 BCG does not have anything to do with selective fire (By that I mean having an M16 BCG will not allow you to have selective fire in a semi-auto only AR). The difference, as far as your semi-auto AR is concerned, is the M-16 BCG has more mass. Some say this helps with cycling in 16-inch carbines. There are no legal concerns with an M16 BCG. If you have a selective fire AR however, then you may have legal concerns with more than just this state (BATFE). Good brands are LMT, BCM and I'm sure there are many more but those are the only ones that come to mind.

Plisk
07-06-2009, 5:40 PM
http://www.fototime.com/C466D2CD5713778/standard.jpg

Top: Colt Semi-auto BCG (different ramp)
Middle: Full auto BCG
Bottom: Semi-auto BCG

These are the differences between full auto and semi auto BCGs. The only function of the 'extra meat' is to engauge the auto-sear on full auto M16s. On an AR15, basiclly its a BCG with extra mass. Some people say it's more balanced, but nothing significant. The semi-auto carriers have 2 advantages in my opinion, one is less wieght, the other is that it's easier to put a new firing pin in because you have more space to work with on the bottom.

Hope this helps!

THT
07-06-2009, 5:49 PM
The full-auto BCG has a shrouded firing pin which results in less stress on the FP and the retaining pin. Some semi-auto's will have a shrouded FP but it depends on the make.

aplinker
07-07-2009, 11:23 AM
The full-auto BCG has a shrouded firing pin which results in less stress on the FP and the retaining pin. Some semi-auto's will have a shrouded FP but it depends on the make.

Good semi's are only different in the cut-away from the M16 carrier, to keep it from being able to trip the auto-sear.

The only advantages of the M16 carrier are:
-generally a known quantity (though a good lineage semi- is equal or better)
-can be used with MG lower out of state (if you have the hook-ups)
-extra ounce of weight, which is good for carbine/pistol gassed uppers.

joelogic
07-07-2009, 11:56 AM
To the OP, the headspace has to do with the barrel not the bcg.

HK Dave
07-07-2009, 3:47 PM
From what I've been told by LMT and Noveske there is no practical difference between the two.

Some people say the extra weight in the M16 carrier helps out with recoil.

Dunno... I can't feel a difference between the two but it could simply be because i don't shoot them side by side comparing recoil.

aplinker
07-07-2009, 5:10 PM
From what I've been told by LMT and Noveske there is no practical difference between the two.

Some people say the extra weight in the M16 carrier helps out with recoil.

Dunno... I can't feel a difference between the two but it could simply be because i don't shoot them side by side comparing recoil.

It's not about what you feel - in fact there should be more perceived recoil with the M16 from reciprocal mass - but about increasing lock time after firing and before the carrier starts to move.

Super Spy
07-07-2009, 5:14 PM
Great Feedback Guys! Thanks!

Justintoxicated
07-07-2009, 5:34 PM
http://www.fototime.com/C466D2CD5713778/standard.jpg

Top: Colt Semi-auto BCG (different ramp)
Middle: Full auto BCG
Bottom: Semi-auto BCG

These are the differences between full auto and semi auto BCGs. The only function of the 'extra meat' is to engauge the auto-sear on full auto M16s. On an AR15, basiclly its a BCG with extra mass. Some people say it's more balanced, but nothing significant. The semi-auto carriers have 2 advantages in my opinion, one is less wieght, the other is that it's easier to put a new firing pin in because you have more space to work with on the bottom.

Hope this helps!

1st does not have a fully shrouded firing pin (and is Semi-Auto / AR15)
-
2nd has more material to the right (slightly heavier) (M16)
- the area on the right is necessary for a full auto to work, but does nothing but add some extra weight for semi auto.
3rd has fully shourded firing pin but is AR15 Style

I use M16 BCG's just because :)

Firing Pin is not really any harder to remove from the M16 BCG since it would be removed from the Open end of the BCG not through the bottom. Once you release the pin it can just fall out on either BCG assembly. If the Advantage of the AR15 style is less weight, then the opposite can be said of the M16 Style (It's advantage is that it has more weight)

Plisk
07-07-2009, 7:10 PM
Firing Pin is not really any harder to remove from the M16 BCG since it would be removed from the Open end of the BCG not through the bottom. Once you release the pin it can just fall out on either BCG assembly. If the Advantage of the AR15 style is less weight, then the opposite can be said of the M16 Style (It's advantage is that it has more weight)

I know removing the pin is the same between carriers, I meant when you put a new one in, in my opinion, it's easier with a semi auto because you can put it into it's hole by hand from the bottom, instead of trying to drop it in from the back.

aplinker
07-07-2009, 7:31 PM
I know removing the pin is the same between carriers, I meant when you put a new one in, in my opinion, it's easier with a semi auto because you can put it into it's hole by hand from the bottom, instead of trying to drop it in from the back.

LOL

Saves, what, a whopping 1/2 second?

1859sharps
07-07-2009, 7:44 PM
The origin of the "semi-auto/ar-15" BCG is political rather then an "engineering brake through".

The "full auto/M16" BCG is what the rifles were originally designed for.