Questions About LMT Enhanced Carrier & Bolt

[MistWolf]

LMT advertises a carrier & bolt that are enhanced and cost a bit more. It's claimed the carrier increases dwell time to delay the opening of the bolt for reduced pressures. How is this delay accomplished? Is the carrier heavier? Or is the timing of the cam slot changed to delay opening the bolt after the carrier has begun it's motion? Or is their something that delays the carrier itself?

Does this carrier offer any real advantages over a standard carrier for a rifle with a rifle length gas system? Does it offer any advantage for a carbine or mid-length gas system? If so, what and is it enough to justify the extra cost? Would you pay the price and use the LMT enhanced carrier, instead of a standard carrier in any of these applications?

LMT claims the enhanced carrier isn't for barrels shorter than 14.5 inches. Is that because the carrier would delay the opening of the bolt too long for reliable functioning?

LMT claims their enhanced bolt gives better support to the case head, has better heat treat and a "more resilient coating". Is it worth the price of admission? Is there a better bolt?

It's a pile of questions but as a technician I want to know how and why things work beyond just being told "because they do!" Thanks

[Thomas M-4]

Post#12 From Bill Alexander is a very good description of the LMT enhanced BCG.
https://www.m4carbine.net/showthread.php?t=3379



LMT claims the enhanced carrier isn't for barrels shorter than 14.5 inches. Is that because the carrier would delay the opening of the bolt too long for reliable functioning?

Grant is using one on his ultimate suppressed sbr it has 11.5'' barrel if my memory servers me correct it doesn't lock the bolt back on a empty mag if the suppressor is removed and also he is using a different gas port size I believe its smaller. I would be careful because there are reports of it not working on LMT 10.5'' uppers just like anything you have to be careful when you go outside the manufactures recommendations.


LMT claims their enhanced bolt gives better support to the case head, has better heat treat and a "more resilient coating". Is it worth the price of admission? Is there a better bolt?

There are a few different company's making a enhanced bolts LWRC & JP come to mind. They have all have had different gens released over the yrs.

[MistWolf]

Thanks for that link. It sounds like the rifle I'm putting together will see no advantage from the enhanced bolt carrier. The LMT enhanced bolt might be worth a closer look

[Evil Bert]

For the LMT enhanced carrier, I am not sure exactly, but from what I can tell (I do not have one), it looks like a standard FA carrier. FA carriers are heavier and increase the dwell time anyway from a non-FA carrier as I understand it. As for the enhanced bolt, the main difference is the extractor. The extractor is similar to the Knight's lobster tail extractor. The pivot point on the enhanced bolt is moved close towards the bolt face and therefore provide more force to the case head for extraction.

[Magic_Salad0892]

I'm going to send a few LMT carriers to be NP3 coated, and they'll be in my Knights guns.

(I've decided I'm going to cut them all to 11'', and have a port drilled, instead of swap barrel extensions, and try to get somebody to make a smaller one for me.

That sounds like a bad idea.)

[militarymoron]

visually, the LMT carrier has a raised ring in front around the bolt hole, 3 ports instead of 2 on the side, and a repositioned hole, also on the left side.

[Thomas M-4]

I run a LMT Enhanced BCG on a 14.5'' LMT upper with a H-buffer with about 3500 + or- rounds through it mostly with xm193 but I have run it with PMC bronze, Wolf steel case 62 grain, 75grain BH blue box and FGMM 69 grain.
Has posted from Bill in that thread it was designed more for durability than reliability. The carrier has to be carefully selected to the barrel length and carbine gas system. I know the carrier is popular with some running a suppressor makes good sense to me because of the extended dwell time before extraction and the ability to deal with excess gas.
I have been contemplating picking up a VLTOR A5 buffer system for the LMT. I believe that having a carrier that it optimized to the carbine gas system with the VLTOR A5 buffer system [std rate rifle buffer spring and correctly weighted buffer] should make for a nice light recoiling carbine.;)

[one]

I've been following the thread that Thomas M4 mentioned for some time now to study Grant's results. Like Thomas it was always my understanding not to use the enhanced carrier with the 10.5.

Some time back I installed a Magpul BAD lever on the gun and immediately various manufacturer's of ammunition became hit and miss on whether or not the bolt would lock back. Since I really do love the BAD lever I've wanted a way to make things all work in sync again.

By the way there was an H buffer in the gun when things started to fail reliability wise. First fix was to go back to a standard buffer and that still wasn't reliable as time went on.

So. I dug out my enhanced LMT carrier from a 16" gun that sits in the safe and installed it. Well. Things changed dramatically. Reliability is right back up where it belongs, including with the now reinstalled H buffer.

This is with both suppressed and unsuppressed use. The can is an AAC M4 1000.

The only thing that I have noticed negative with the LMT enhanced is that it would not allow Magpul 20 round magazines to seat and lock into the gun. 30's do just fine but not the 20's. Since the 20's are reserved for my SPR build it's not really an issue for me but could be something someone else reading this thread might find useful to know beforehand.

[DBR]

I have the enhanced carrier in my Colt 6721 CAR gas 16" carbine. It is my understanding that the enhanced carrier was intended for the CAR gas system on a 16" barrel. It has a different shaped slot for the cam pin that allows the carrier to travel a bit more before it rotates the bolt and it vents the gas differently.

I have had reliable operation with it and I think the gun shoots softer. When it first came out some were having short stroking on CAR 14.5 barrels. I don't think it would have any benefit on a rifle length system and probably would be less reliable than the stock carrier.

[payj]

From what I get from it is the carrier is designed more or less for sbr's. The bolt itself could be looked at as an improvement/upgrade to any AR....

[gbackus]

From what I get from it is the carrier is designed more or less for sbr's. The bolt itself could be looked at as an improvement/upgrade to any AR....


Quite the opposite, the carrier is designed for the 14.5-16" carbines, and is not recommended on barrels shorter than 14.5"

[payj]

Yeah your right. Had it confused.......

This has been discussed a few times. Here is another thread on the carrier/bolt:

http://m4carbine.net/showthread.php?t=3379&highlight=enhanced

[Thomas M-4]

Yea the specs say 14.5''-16'' barrels with carbine gas system I also believe it is recommend to use 5.56 pressure ammo. Which is fine with me because I shoot alot of 5.56 but I have put a good bit of .223 stuff also. PMC Bronze and Federal bulk pack mostly. I did have a couple of short strokes on Remington UMC that stuff is weeeak I am fairly certain wolf has more thump than that crap.

[Thomas M-4]

I have the enhanced carrier in my Colt 6721 CAR gas 16" carbine. It is my understanding that the enhanced carrier was intended for the CAR gas system on a 16" barrel. It has a different shaped slot for the cam pin that allows the carrier to travel a bit more before it rotates the bolt and it vents the gas differently.

I have had reliable operation with it and I think the gun shoots softer. When it first came out some were having short stroking on CAR 14.5 barrels. I don't think it would have any benefit on a rifle length system and probably would be less reliable than the stock carrier.

Never mind I reread your post.

[Thomas M-4]

Well I wanted to give an update just got back from the range today.
Met up with a buddy that has a 10.5'' Novoske switch block upper I finally got to swap carriers around. I can tell you that with a enhanced carrier and the 10.5'' switch block set to suppressed with installed suppressor is the softest shooting combo I have felt to date. We only used 5.56 ammo but it did cycle fine we put about 150+or- didn't keep exact count sorry was having to much fun. past it around to another shooter and first comment he said was how soft cycling it was. We did have a few failures to lock the bolt back on a empty mag with out the suppressor but other than that it worked great.

[one]

That's interesting to me. I was able to fix my bolt failing to lock back without a suppressor via the enhanced carrier.

I'd love to have access to a switch block upper to try.

[Heavy Metal]

visually, the LMT carrier has a raised ring in front around the bolt hole, 3 ports instead of 2 on the side, and a repositioned hole, also on the left side.

And an altered cam slot.

The rifle lengths gas system does not need this part and may not work with it. A carbine or an over-gassed middy would run it but stay away from it in a rifle and beware it in a really short barreled carbine.

It is designed to run in 14.5 inch carbine gas systems and will work with 16 inch carbine systems. Anything else, YMMV.

[Magic_Salad0892]

We did have a few failures to lock the bolt back on a empty mag with out the suppressor but other than that it worked great.

That's how it should be (unsuppressed) on a suppressed weapon, IMHO.

[pleaforwar]

It is designed to run in 14.5 inch carbine gas systems and will work with 16 inch carbine systems. Anything else, YMMV.
Guess I run under the "YMMV" category. I am very happy with my LMT enhanced bcg running in my 16" midlength. :D

[Thomas M-4]

That's interesting to me. I was able to fix my bolt failing to lock back without a suppressor via the enhanced carrier.

I'd love to have access to a switch block upper to try.

I didn't take a note book with me :( and we where running xm193 and m855 with out paying attention to exactly every detail [was having too much fun]. But with the suppressor removed and the switch block switched to non-suppressed it would cycle through 30 rounds no problem but the bolt would fail to lock back. I believe that would be because of the shorter dwell time the gas port being so close to the end of the barrel. With the suppressor attached and the switch block set to suppressed it would lock back the bolt every time. The suppressor is artificially increasing the dwell time even though the switch block is restricting some of the gas pressure.
I have to re-read the best suppressor thread but I believe that is what was happening. If you get a chance to try a 10.5'' switch block with a suppressor please try it with enhanced carrier it is stupidly soft cycling when the switch is on suppressed .

[Thomas M-4]

That's how it should be (unsuppressed) on a suppressed weapon, IMHO.

I can understand why it is doing it and I also see your point of view on it.
But I cant help but wonder if the Vltor A5 buffer system might change that having the constant rate rifle length buffer spring could make it more forgiving. But that is just a SWAG on my part.

[one]

I don't think the switch block will fit and be accessible under the DD RIS II will it? That's what I'm running on here now.

I would love to try one out on a gun capable of it.

[chadbag]

Quite the opposite, the carrier is designed for the 14.5-16" carbines, and is not recommended on barrels shorter than 14.5"

The Complete LMT Enhanced BCG is not recommended for rifles less than 14.5". That is enhanced carrier and enhanced bolt.

Some people use the enhanced carrier with a standard bolt on SBRs shorter than 14.5. That is a different question than what LMT states which is the complete BCG.

[Thomas M-4]

I don't think the switch block will fit and be accessible under the DD RIS II will it? That's what I'm running on here now.

I would love to try one out on a gun capable of it.


I don't think so not with out cutting the rail:bad:

[one]

I was sure it wasn't small enough and protrude enough out the front. I haven't even looked at pics of a switch block in ages.

To clarify on my set up it's enhanced carrier and standard bolt. So far it's the only set up that's allowed the gun to run 100% (with the BAD lever installed that is).