LMT S/A and F/A BCG: operations question

[dennyAC170]

I have ordered a LMT 16" upper with standard S/A BCG and have a few questions:

1. Is the following correct? S/A or semi-auto BCG is an AR-15 style bolt carrier
and the F/A or full-auto is the M16 style bolt carrier.

2. What is the difference in functioning between the two types of carriers?

3. Is the full-auto bolt carrier more reliable with a wider variety of loads?

4. If I use Hornady 5.56 75-gr TAP, would I be better off with the F/A BCG?

Thanks in advance.

I did search for related threads and found some information.

[faithmyeyes]

Not having actually handled very many of them, I'm not as qualified as others to give you an authoritative answer - but I'll share what I believe is correct:


1. Is the following correct? S/A or semi-auto BCG is an AR-15 style bolt carrier and the F/A or full-auto is the M16 style bolt carrier.
Have you seen this thread (https://www.m4carbine.net/showthread.php?t=14534) on AR-15 vs. M16 style carriers? I believe the LMT semi-auto carriers are the "enhanced AR-15" type, which are not as heavy as the M16 carriers but do shroud the firing pin.


2. What is the difference in functioning between the two types of carriers?
The FA carrier is heavier. This will slightly increase cycle time, and help slightly to absorb recoil impulse. There may be some thermal benefit as well, which would probably only really matter in a FA gun. I'm not aware of any functional difference beyond the added mass, but someone who's actually worked with the FA carriers would know better than I.


3. Is the full-auto bolt carrier more reliable with a wider variety of loads?
I've been told that a FA carrier adds marginally to the overall reliability of the gun, depending somewhat on how the entire weapon system is configured. Whether a FA carrier would make some loads run well that might not with a SA carrier... I tend to instinctively doubt it, but I honestly don't know.


4. If I use Hornady 5.56 75-gr TAP, would I be better off with the F/A BCG?
See #3.

Good luck...