bohica793
Master
What is the difference between a full auto Bolt Carrier Group and a semi-auto? Is there a visible difference that you can use to differentiate the two?
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Stupid question
- Thread starter bohica793
- Start date
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Fishyfingers
Expert
SAWMAN
Master
Weight of carrier and cutout at the rear part of the carrier. IIRC those are the only differences. --- SAWMAN
pavegunner1
Expert
Excellent info and all these years of firing this platform I never knew
bohica793
Master
Ok, now what is the practical useful difference?
Crazydoc68
Almost a doctor
Only if you are firing full auto. Just a few extra ounces of weight. Just my .02
FrankT
6.8 SPCII Hog Slayer
It adds some weight to your bolt carrier and strengthen it slightly, which is the reason that I like to go with FA bolt carriers...there is no practical reason just preference. I think it makes the recoil smoother and you have a full firing pin shroud.
oneshot
Master
Thanks FrankT. As the title sad. just my 5 cents jj
SAWMAN
Master
Sometimes the diff in weight will make a diff in the guns "dwell time". (bbl length vs gas port location vs gas port opening vs gas block position vs moving mass of the BCG) It definitely did with my 10.5" 6.8 and the carbine gas. In the AR's and other "rifles" it is all about the speed of the BCG. Too slow could be bad as could too fast.
This is why it is critical to match the different parts of the system to each other. A store bought AR has this already done for the end user. When you start piecing different parts together from different guns and/or different manufacturers it makes a big difference.
These are some of the AR parts that have to work together properly.
* BCG (mainly it's weight) (moving mass).
* BBL length.
*What position the gas port is in in relation to the length of bbl.(pistol,carbine,mid,rifle)
* size of gas port in bbl
* Different gas blocks and their relation to their position over the bbls gas port.
* to a certain extent,the gas tube
* Ammo used as far as power(produced gas and at what speed)
* powder used to propel the bullet.
* Magazine used. How it seats in the mag well and the shape of the feed lips. This goes directly to BCG speed.
* How clean or dirty is the gun and how well lubed ??
Just a guess but,probably how the weapon is shouldered. I would think that some rifles could be "limp wristed" and/or bump(inertia)fired. --- SAWMAN
This is why it is critical to match the different parts of the system to each other. A store bought AR has this already done for the end user. When you start piecing different parts together from different guns and/or different manufacturers it makes a big difference.
These are some of the AR parts that have to work together properly.
* BCG (mainly it's weight) (moving mass).
* BBL length.
*What position the gas port is in in relation to the length of bbl.(pistol,carbine,mid,rifle)
* size of gas port in bbl
* Different gas blocks and their relation to their position over the bbls gas port.
* to a certain extent,the gas tube
* Ammo used as far as power(produced gas and at what speed)
* powder used to propel the bullet.
* Magazine used. How it seats in the mag well and the shape of the feed lips. This goes directly to BCG speed.
* How clean or dirty is the gun and how well lubed ??
Just a guess but,probably how the weapon is shouldered. I would think that some rifles could be "limp wristed" and/or bump(inertia)fired. --- SAWMAN
bohica793
Master
Well, I am planning on an 18-20" barrel, rifle length gas system. If I need to go lighter or heavier is fine, just want to choose the right one for the job.
TackleberryMCS
Master
I agree with Frank on this one. I try to use nothing but M16 BCGs on most all of my ARs with a few exceptions.
TackleberryMCS
Master
You cannot go wrong with a M16 BCG. All of the retro ARs (carbines and rifles) I have built have M16 BCGs. Most of the modern ARs I have built have M16 BCGs. I have never had issues with any of them. Even with my latest 14.5" mid-length, I use a NiB M16 BCG and a standard BCM carbine buffer. I works as smooth as silk.
SAWMAN
Master
Out of all the MAJOR AR manufacturers how many supply their weapons with a full auto carrier ?? Why or why not.
And ..... "strengthen it slightly" ............. Do the non full auto carriers tend to bend or break at the rear section ??
(I have a full auto carrier in my 10.5" AR "pistol".) --- SAWMAN
And ..... "strengthen it slightly" ............. Do the non full auto carriers tend to bend or break at the rear section ??
(I have a full auto carrier in my 10.5" AR "pistol".) --- SAWMAN
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FrankT
6.8 SPCII Hog Slayer
Stag and RRA give you an upgrade option for the FA So I am guessing you can upgrade any rifle from most MFG
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 bolt 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.
https://spreadsheets.google.com/pub?key=pwswheghNQsEuEhjFwPrgTA&single=true&gid=5&output=html
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 bolt 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.
https://spreadsheets.google.com/pub?key=pwswheghNQsEuEhjFwPrgTA&single=true&gid=5&output=html
As soon as I clicked on this I figured that "The Chart" was going to come out.
I'm with Frank though, every single one of my AR's have a FA BCG in them. If you run a semi auto bcg hard enough you can bend the firing pin. I've never had it happen personally but I've heard enough stories, real or made up, that it's just cheap insurance for me. Also except for my KAC rifles I use BCM bcg's exclusively so it's kind of a mute point as I am not even sure they make a semi one.
I'm with Frank though, every single one of my AR's have a FA BCG in them. If you run a semi auto bcg hard enough you can bend the firing pin. I've never had it happen personally but I've heard enough stories, real or made up, that it's just cheap insurance for me. Also except for my KAC rifles I use BCM bcg's exclusively so it's kind of a mute point as I am not even sure they make a semi one.
