I did a search but with 32 pages of responses to query I gave up.

Anyway, I understand the difference between full-auto and semi-auto bolt carriers. My question is does it really matter in an AR-15? Does it impact reliability, durability, etc.? I've heard some say the recoil impulse is different but I'm not expert enough to notice that.

Put another way, I have an LMT with a semi-auto bolt. Would you buy a full-auto bolt or be happy with the semi-auto and let it be? I've also got a Toolcraft full-auto bolt in my parts bin but I'm struggling to see why I should swap it out with the OEM bolt in my LMT.

Thoughts?

As long as it's a quality BCG that's in-spec with properly staked gas keys, semi vs. full matters not one bit.

I have had guns with both types and never noticed any difference in operation.

As RogueJSK states, the most important thing is in-spec with properly staked keys. There's really not much difference in how a semi vs. full functions.

That said, the slightly additional weight of the full auto carrier does slightly slow the cycling process. Similar in concept -- but generally not as effective as -- to a heavier buffer and/or stronger spring. If your AR is over gassed, the full auto carrier might help a bit. Or maybe you won't any significant difference.

Isn't most of the difference is in weight ?

I have both kinds, it makes no difference.

I only care if the hardness and staking is correct. All my vintage Colt parts are magnetic particle tested.

quote:

Originally posted by BB61:
I have an LMT with a semi-auto bolt.

You have an LMT with a semi-auto carrier.

You have everything you need with that BCG, which is a high-quality part.

You can (but don't necessarily need to) compensate for the reduced weight of your carrier, with a heavier buffer. If you are using an H buffer, install an H2. If you're using an H2 buffer already, you're all set. This assumes you're using this BCG in the ubiquitous 16" barrel, carbine-length (and probably over-gassed) gas system.

Reduced carrier weight becomes a factor only when we're talking about the Colt post-ban carriers, which were horribly neutered.

To understand what I'm referring to, go here. Check page 2 of that thread for a pic of the difference.

^^^
Thanks Boss for the correction and info/link!

My LMT is stock. It’s older but stock.

Thanks to everyone else as well.

When I had LMT ARs, they all had their factory semi-auto BCG, and they all worked just fine. LMT makes great stuff. Love their original MRP.

Having a full auto carrier sounds cooler.

Seriously though, I agree with everything else said. No difference with quality parts.

It never used to actually matter. The only reason it may actually matter going forward is that a full auto carrier is required for an FRT or Super Safety to function. If you're not messing with one of those, then all the other replies cover it.

Well, a full auto bolt carrier is heavier, so depending on your loading, if you want a FRT, esetra. One is better than the other.

I, myself prefer a full auto BCG, but a high quality semi-auto BCG isn't a worry.

I'm a mil-spec or better kind of guy, so to me, if it meets Mil-Spec or better, is full auto rated or better that's me.

But quality parts is quality parts!


ARman

You're fine with the semi-auto carrier in the LMT. The auto is more money. Mine (LMT Defender) works just fine with a semi-auto BCG in there.
Good luck in finding the enhanced bolt & BCG from LMT! Those things have been unobtainimum for a few years now!