AR15.Com Archives
 Full auto vs. Semi Auto bolt carrier
johnnyyork  [Member]
12/17/2007 5:00:30 PM EST
Whats the difference between a F/A BCG as compared to a S/A BCG.

Thanks
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LoneWolfUSMC  [Member]
12/17/2007 5:12:26 PM EST
Someone will come along soon and post "the pic" of the carriers side by side.

Basically there is more metal in the right places and more mass overall. You DO want the M16/Full Auto Carrier. NO they are NOT illegal in an AR15.
yoteslaya  [Member]
12/17/2007 5:22:41 PM EST
This is the difference.

Alpha-Romeo3  [Team Member]
12/17/2007 5:40:04 PM EST

Originally Posted By johnnyyork:
Whats the difference between a F/A BCG as compared to a S/A BCG.

Thanks




The M16 bolt carrier will have about a 2" closed section at the rear that actually trips the auto sear in full-auto fire. Semi-auto versions have either a reduced closed bottom section (about 1/2"), or a completely open bottom (made so that an adapter to M-16 configuration cannot be installed).



Another difference in the bolt carriers is the additional metal removed on the underside to expose the collar of the firing pin. This is intended to catch the hammer and prevent firing if the carrier is not fully forward when the hammer releases. This occurs if the hammer is "riding" the carrier back (i.e. no auto sear is holding back the hammer). On the M16 bolt carriers, the firing pin collar is not exposed.

There are some "hybrid" carriers that do not have this area open and yet only have the 1/2" closed bottom section in the back. There are others that appear to be M16 carriers, but apparently have had 1/4" of the rear "sear trip" section milled, and so do not qualify as M16 carriers because they cannot trip a sear.


More info here: AR-15 Vs. M16 Parts link
ALPHAGHOST  [Team Member]
12/17/2007 5:46:13 PM EST

Originally Posted By Alpha-Romeo3:

Originally Posted By johnnyyork:
Whats the difference between a F/A BCG as compared to a S/A BCG.

Thanks



www.ar15.com/content/legal/ar15-m16parts/boltCarrier.gif
The M16 bolt carrier will have about a 2" closed section at the rear that actually trips the auto sear in full-auto fire. Semi-auto versions have either a reduced closed bottom section (about 1/2"), or a completely open bottom (made so that an adapter to M-16 configuration cannot be installed).


www.ar15.com/content/legal/ar15-m16parts/boltCarrier2.gif
Another difference in the bolt carriers is the additional metal removed on the underside to expose the collar of the firing pin. This is intended to catch the hammer and prevent firing if the carrier is not fully forward when the hammer releases. This occurs if the hammer is "riding" the carrier back (i.e. no auto sear is holding back the hammer). On the M16 bolt carriers, the firing pin collar is not exposed.

There are some "hybrid" carriers that do not have this area open and yet only have the 1/2" closed bottom section in the back. There are others that appear to be M16 carriers, but apparently have had 1/4" of the rear "sear trip" section milled, and so do not qualify as M16 carriers because they cannot trip a sear.


More info here: AR-15 Vs. M16 Parts link


thx

i was having a tough time pulling that one up...
johnnyyork  [Member]
12/18/2007 5:18:56 AM EST
Thanks for all the great help and information and both the great sets of pics. I see the physical differeneces, if makes more since to me. I understand that the M16 is heavier and will be more durable. I ordered one recently and wanted to know the difference.

One last question... Lone Wolf USMC said that I would want an M16 BCG:



Originally Posted By LoneWolfUSMC:
Someone will come along soon and post "the pic" of the carriers side by side.

Basically there is more metal in the right places and more mass overall. You DO want the M16/Full Auto Carrier. NO they are NOT illegal in an AR15.


Besides durability, what are other advantages? Also, is there anytime one would choose an AR15 carrier over an M16.

Thanks for all the help!
GONIF  [Member]
12/18/2007 7:50:56 AM EST
I can't imagine an advantage to the semi bcg, the BCM M16 bcg that Bravo has for $130.00 is what will give you the best quality and value .
Stallion1  [Member]
12/18/2007 9:04:58 AM EST
I think Bushmasters come with the M/16 BCG, I could be wrong though. Nope looked on the site I'm wrong.
knight_dive  [Member]
12/22/2007 8:28:23 AM EST
Ok, I'm confused. Lonewolf USMC says that Auto BCGs are not illegal in semi's and I've heard that some Colt semi models come w/ Auto BCGs, but isn't the ar15 vs M16 parts thread saying they are illegal?
Molon  [Team Member]
12/22/2007 8:49:32 AM EST

Originally Posted By knight_dive:
Ok, I'm confused. Lonewolf USMC says that Auto BCGs are not illegal in semi's and I've heard that some Colt semi models come w/ Auto BCGs, but isn't the ar15 vs M16 parts thread saying they are illegal?



Put a full-auto carrier in your semi-auto AR-15 and tell me wether or not it fires full-auto.
knight_dive  [Member]
12/22/2007 9:08:48 AM EST


Put a full-auto carrier in your semi-auto AR-15 and tell me wether or not it fires full-auto.


yeah, I understand the mechanics of it, but its this part of the AR15 vs M16 parts thread that has me concerned:

"Conclusion
As mentioned previously, having M16 parts in you AR does not mean that it will be capable of automatic fire, but it does mean that you could be in violation of the law."

GarrettJ  [Team Member]
12/22/2007 9:14:17 AM EST

Originally Posted By Stallion1:
I think Bushmasters come with the M/16 BCG, I could be wrong though. Nope looked on the site I'm wrong.

I built a rifle from a BM kit 10 years or so ago. Their carrier that came with it has the standard AR15 back end (full circle, but shortened so as to not trip a DIAS), and it has the cutout at the firing pin.

Not sure if they have made any changes since then.
DON70  [Team Member]
12/22/2007 11:23:35 AM EST

Originally Posted By knight_dive:


Put a full-auto carrier in your semi-auto AR-15 and tell me wether or not it fires full-auto.


yeah, I understand the mechanics of it, but its this part of the AR15 vs M16 parts thread that has me concerned:

"Conclusion
As mentioned previously, having M16 parts in you AR does not mean that it will be capable of automatic fire, but it does mean that you could be in violation of the law."






While there may be some benefit to using an M16 carrier it's not worth the risk to me.
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