Simple AR question

From my understanding, the full-auto (M-16) bolt carrier is slightly heavier, making the recoil and cycling ever-so-slightly softer in a semi-auto AR.

I have a full-auto bolt carrier in my semi-auto Spikes carbine, and I've never had a problem with it. It's a great-shooting gun all around.
 
M16/Auto BCG is the one without the cutout on the bottom of the carrier.
The semi has the cutout to prevent from tripping the auto sear in.
In a semi-auto AR (missing the auto sear), function will not be affected by the difference in BCG.
Heavier BCG slows down cyclic rate. I do not shoot fast enough to notice in my semi-auto carbine.
I like the heavier (full-auto) version because I think it will absorb more recoil than the lighter version.
if you already have version X, I would not recommend replacing it with version Y. I do not think there is significant performance difference in a semi-auto.
 
if you haven't bought one yet- get whichever is cheaper/available at the time.
It really does make zero difference in a semi-auto AR.
 
There are several different semi-auto carriers, so the difference depends on which one you are comparing. Typically, a semi-auto carrier has a bigger cutout that does not hold down the hammer as long as an M16 carrier. As a result it is a bit lighter and can unlock a few nanoseconds earlier. The other common difference is that not all semi-auto BCGs have a firing pin shroud to keep the hammer from hanging on the firing pin collar if it follows; however they make semi-auto shrouded BCGs.
 
The other common difference is that not all semi-auto BCGs have a firing pin shroud t

+1 on this statement! I use AR16 BGC'S in all of my AR15 builds:D
 
I believe all "new" bolt carriers are shrouded design, no one has made the unshrouded in years. You well still see used ones around.

The weight difference between a semi auto BC and a full auto BC is less than 12 grams. You well see a insignificant difference in a normally functioning AR.

I would not pay extra for the FA BC.
 
>>The weight difference between a semi auto BC and a full auto BC is less than 12 grams.

That's a little under half an ounce. If you look at the difference between the H, H2, and H3 buffer specs they usually increase in .4oz to .6oz steps; so that 12 grams can make a difference in the dwell time between cycles.

Here is a link that has some charts explaining the AR15 gas system and "dwell time".

http://ar15barrels.com/prod/operation.shtml

A milspec M16 bolt carrier is going to cost you the same amount as a semi version. ($100-130 from BCM, Spikes, Rainier Arms) If you have the typical 16" carbine with a standard carbine length gas system the extra weight in the carrier will help slow down the cycle rate; it would probably even be a good idea to go with a heavy H1 or H2 buffer. If you have a mid length gas system a normal carbine buffer will be just fine.

IMHO, if you're looking at replacing the BCG I would go with a Nickel Boron (NiB) coated system as they are super slick, require almost no lube, and clean up with a paper towel. No more scraping carbon.

Keep in mind with every Tom, Dick and Harry churning out AR parts these days it's easier to find a milspec full auto carrier online than it is to find a semi version. I know some of the commercial grade manufacturers, i.e. RRA and DPMS, still use the semi carriers.

Good luck.
 
CLC

Simple AR question
Should I buy a semi or auto BCG for my build? Whats the difference in a semi rifle?
Click to expand...

where do you live ? some states have a full auto ban, if you decide to go with a semi.., i have several Colt BCG's some stripped and some ready to install.
 
Thanks alot for all the help. The reason I ask is my 16" BCM Carbine length upper didn't come with a bolt. I live in PA if that helps.
 
>>where do you live ? some states have a full auto ban, i

This is complete misinformation. Per the ATF, the "full auto" version of the carrier does not make it a machine gun.... :rolleyes:
 
the full auto is rated for full auto, the semi is not. it's different levels of construction. if you are going to be shooting thousands of rounds per range day and doing that consistantly then the FA will be a wise choice but if you are shooting a few dozen rounds per outting and only shooting a couple times a week then the SA will work just fine.
 
tahunua001 said:
the full auto is rated for full auto, the semi is not. it's different levels of construction.
Click to expand...

The main issue is that the semi-auto carrier has a larger cutout on the bottom of the carrier. The metal on the bottom of the carrier is what holds the hammer down while the bolt cycles. You can run a semi-auto carrier in a full-auto upper and it will do just fine durability wise - the problem will be that you'll have lots of stoppages because the hammer hit the firing pin before the bolt could get back in battery.

The M16 cutout holds the hammer down longer to insure more reliable function in full auto.

sailskidrive said:
This is complete misinformation. Per the ATF, the "full auto" version of the carrier does not make it a machine gun....
Click to expand...

This is correct. ATF will tell you that you can have as many M16 parts in a rifle as you want as long it does not meet the statutory definition of a machinegun.

The concern from a legal perspective is that the statutory definition of a machinegun as used by ATF is "any gun that fires more than one round with a single function of the trigger." So a weapon that fires a burst as a result of worn parts is as much of a machinegun as one that was illegally converted. If you happen to get caught in such a situation and then you do have actual machinegun parts in the rifle (especially if the rifle doesn't ship from the factory like that), you can be in awkward position.

Of course, that is a pretty easy situation to avoid with regular inspection and maintenance; but a lot of AR problems are easy to avoid with regular inspection and maintenance and people seem to find them all the time anyway.
 
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