View Full Version : LMT ENHANCED CARRIER, EARLY UNLOCKING?
Hey guys,
Short and sweet.
Ive got a 13.7 inch, midlength gas build that I just put together. Ive had an LMT enhanced carrier sitting around that I originally ordered for a BRT barrel that never materialized. I decided to slap that in there and head to the range.
The gun functioned 100% but brass ejection was erratic. It would eject a round or two to 4 o'clock then randomly throw one or two casings to 1 o'clock. Again, the gun functioned well but the erratic nature of the brass ejection caused me some concern.
I swapped in a normal, full auto M16 carrier and the brass ejection pattern changed to a 100% consistent 4 o'clock ejection.
Thoughts on this guys? I "feel" like the gun shot softer with the LMT carrier but that could be all in my head. Obviously I'm chasing feel AND function with this build so id like the softest shooting, most reliable carbine possible.
Try the LMT carrier with the bolt from the full auto carrier. The erratic ejection pattern is likely due to a weak extractor spring or a weak extractor spring combined with a weak ejector spring. If the LMT carrier has an LMT enhanced bolt, there's a good chance the extractor springs are weak. I have an early LMT e-bolt that had weak extractor springs (the bolt uses dual springs) and wouldn't properly eject. A weak extractor spring means the extractor won't hold the case against the bolt face and compress the ejector.
Try the LMT carrier with the bolt from the full auto carrier. The erratic ejection pattern is likely due to a weak extractor spring or a weak extractor spring combined with a weak ejector spring. If the LMT carrier has an LMT enhanced bolt, there's a good chance the extractor springs are weak. I have an early LMT e-bolt that had weak extractor springs (the bolt uses dual springs) and wouldn't properly eject. A weak extractor spring means the extractor won't hold the case against the bolt face and compress the ejector.
Im tracking.
IF this is the case, does anyone say, Wolf, make a stronger extractor spring? Are the dual extractor springs simply milspec springs or are they proprietary? I haven't taken it apart to look as im on duty for a few more days so I figured I would ask here.
I don't think anyone outside of LMT really knows exactly how they're made, but it's speculated they might be made from cut down ejector springs. The width is identical as I recall.
Tubb makes an extra power ejector spring, but it's made out of chrome silicon. If you cut them, the improvised extractor springs will be uncoated on the ends, which isn't really great so far as corrosion is concerned. I've heard people have had success with just creating new dual springs from a normal stainless ejector spring.
Alternatively, you could try just buying a few sets of enhanced extractor springs from LMT and finding a pair that gives the desired extractor tension.
I posted this pic a while back.
Top:Ejector/Safety Select Spring
Middle:LMT Dual extractor springs
Bottom:Takedown/Pivot springs
https://www.m4carbine.net/attachment.php?attachmentid=54138&d=1539470915
I have a had a few reliability issues with LMT enhanced bolts. Never them braking.
But... I have had ejection/extraction issues that were fixed with new extractor springs and a new extractor. The extractor looked good, I replaced as a course of action.
one was on a bolt with 6000+ rounds on it, idk it I didn't track it. I have a bad habit of not tracking round counts on ware parts like springs and often don't replace then until the cause malfunctions. I should be better, I'm not.
The other was a brand new bolt and barrel, again I replaced both, idk if it was springs or extractor. This one had more extraction issue than anything, it was probably a bad extractor from the factory.
LMT bolts are awesome, but need the springs and probably extractor replaced every 5000 rounds I'd guess.
Are KAC springs the same dimensions as the LMT?
With all the craziness in my life lately, haven't had a chance to follow up with this suggestion that member Vulcan5 PMed me awhile back. It sounds like a good solution to the ebolt extraction issue-
MistWolf,
Apologies, I just saw this..............
I exclusively run LMT 5.56 enhanced bolts, the old ones....................
You can cure the *extraction* problems by using the 6.8 enhanced bolt extractor springs listed on the LWRCI website. These are the only compatible springs listed that will work, as LWRCI no longer makes their 5.56 enhanced bolts which were made under license from LMT anyway.
The LWRCI 6.8 extractor springs are a little longer and stiffer than the LMT replacement springs and the LWRCI springs are buffered as they have viton rubber inserts inside them. I use them all the time with no issues, but a little PITA to re-install the extractor pin in the bolt due to more spring pressure.
You may want to also examine the type of roll pin LMT used to secure the ejector. I am sure you know there are 2 types, listed as long and short. ALL of mine came with the short pin which IMHO is a NO-GO.
RARELY, but possible, depending on the install the short pin can interfere with ejector movement and sometimes even lock the ejector to the rear, ask me how I know! Therefore I have replaced all my ejector roll pins with the long ones. Try to get the open part of the roll pin opposite of the bearing surface it comes in contact with on the ejector.
Hope this helps.
Vulcan5
To be honest this seems like an overkill for a very expensive bolt which should work thousands, if not 10's of thousands of rounds out of the box. The more reviews and experiences I read about LMT enhanced bolt and BCG the more i'm inclined to think it's not a duty grade product. If I'm not mistaken LMT does not use them in any of their rifles out of the factory.
Inconsistent ejection, extraction, bcg running fast or slow depending on barrel length/port size/buffer weight/etc. Proprietary springs which have issues either out of the box or after a few K rounds, etc. I'm not sure if they are addressing any actual problem with it (vs a milspec bolt) or just selling it based on a marketing alone. Even if they are addressing some of deficiencies in theory, execution seems far from proper for a Tier-1 company.
Compared to a number of BCM/Colt/DD BCGs/Bolts out there vs LMT enhanced it seems like issues constantly come up with LMT even in number count (in percentage terms that would be a few orders of magnitude more). Or is it just seems to me that way?
Couple thoughts on the bolt issues.
The bolts really do seem to last a long time before catistoohic failure. Mil spec bolts not so much.
I think part of what we are seeing is where a mil spec bolt may have need totally dead, the LMT bolt just wore its ware items and needs a refresh. Realistically the action spring should be replaced every 5000 rounds, why not the ejector and ejector springs at the same time? Do people buy LMT bolts expecting it go forever and not ever ware a spring? Maybe
Secondly maybe they are finicky in ways. Obviously the extractor spring is the weakest part. But, if the above posted quote is correct about LWRCI 5.56 advanced bolt being a licensed LMT, something to consider is the trouble LWRCi had producing them.
The story is the bolts had reliability issues, not from breakage but malfunctions. The issue was tolerances. Their quite good Japanese CNC machine was not accuarate enough to make them to the necessary tolerences. LWRCi eventually gave up. Could LMT bolts be difficult to produce and cause malfunctions if not? Maybe, but it seems all issues are in the extractor and it’s springs. Not the bolt body.
Just to clarify, the rifle extracts and ejects, its just horribly erratic.
In MY particular instance, I think that Mistwolf is on track with the extractor and ejector springs being weak. Thus far, the bolt is not wearing prematurely but it also only has 250 rounds on it so IF It were wearing id be seriously concerned.
Its going to be a bit before I can make it to the range but ill try a milspec bolt in the LMT carrier.
Silly question, when it ejects more forward, have those rounds been sitting in a hot chamber slightly longer than the others? I’ve noticed that that can have an effect.
FWIW, my LMT E bolt has consistent ejection in a 16” extended midlength gas rifle. Its been in there for 3,920 rounds.
Edit: Enhanced bolt only, in a FCD carrier. Sample of one. Reading below, it looks like the problem may have more to do with the enhanced carrier.
The gun functioned 100% but brass ejection was erratic. It would eject a round or two to 4 o'clock then randomly throw one or two casings to 1 o'clock. Again, the gun functioned well but the erratic nature of the brass ejection caused me some concern.
I swapped in a normal, full auto M16 carrier and the brass ejection pattern changed to a 100% consistent 4 o'clock ejection.
Thoughts on this guys? I "feel" like the gun shot softer with the LMT carrier but that could be all in my head. Obviously I'm chasing feel AND function with this build so id like the softest shooting, most reliable carbine possible.
I did a test of my own today with one of my AR's to try to mimic your experience.
Upper specs:
-16" Noveske CHF w/pinned GB
-Noveske Chainsaw Gen 1 upper
-Geissele MK4 13"
-VLTOR VC-1 FH
Lower Specs:
-Rainier Arms forged lower
-LMT 2-stage trigger
-BCM RE w/H2 buffer
I did a 5-shot test of each setup with Winchester White box 5.56 55GR.
-1st test- LMT semi-auto Enhanced carrier w/FN bolt(MPF marked w/copper colored extractor)
-2nd test- Full-Auto Mil-spec carrier(KAC SR15 takeoff) w/FN bolt(same as above)
Results:
1st test-erratic ejection from 3 o'clock to dribbling at 1 o'clock. Failed to lock back on 20rd mag(Colt)
2nd test-strong ejection from 2:30 to 3 o'clock. Locked back on last round.
I'd wonder if you can take the rubber inserts out of the LWRC springs, cut them down a little, and fit them onto a new replacement pair of LMT springs?
Seems like a decent way to offer a bit of reinforcement without risking excessive extractor tension. I would assume that, with the longer dwell time and more aggressive extractor claw, the EBCG doesn't need quite as much tension to begin with.
To be honest this seems like an overkill for a very expensive bolt which should work thousands, if not 10's of thousands of rounds out of the box. The more reviews and experiences I read about LMT enhanced bolt and BCG the more i'm inclined to think it's not a duty grade product. If I'm not mistaken LMT does not use them in any of their rifles out of the factory.
Inconsistent ejection, extraction, bcg running fast or slow depending on barrel length/port size/buffer weight/etc. Proprietary springs which have issues either out of the box or after a few K rounds, etc. I'm not sure if they are addressing any actual problem with it (vs a milspec bolt) or just selling it based on a marketing alone. Even if they are addressing some of deficiencies in theory, execution seems far from proper for a Tier-1 company.
Compared to a number of BCM/Colt/DD BCGs/Bolts out there vs LMT enhanced it seems like issues constantly come up with LMT even in number count (in percentage terms that would be a few orders of magnitude more). Or is it just seems to me that way?
It's just that way to you.
They can't keep them in stock, and it's been that way for years.
Silly question, when it ejects more forward, have those rounds been sitting in a hot chamber slightly longer than the others? I’ve noticed that that can have an effect.
FWIW, my LMT E bolt has consistent ejection in a 16” extended midlength gas rifle. Its been in there for 3,920 rounds.
Edit: Enhanced bolt only, in a FCD carrier. Sample of one. Reading below, it looks like the problem may have more to do with the enhanced carrier.
Yes and no.
On a cold gun, first string of rapid fire with the LMT Enhanced bolt, the gun ejected erratically as described.
As the gun heated up, no change. The Enhanced bolt carrier was consistently erratic if that makes any sense lol. The standard BCG was consistent in its ejection regardless of chamber temperature.
MikhailBarracuda91
01-08-20, 09:35
My brother just had ACDO put together an enhanced M4A1 using LMT stuff. The EBCG has perfect ejection pattern, and everything runs as I would expect. The rifle literally has no recoil
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My brother just had ACDO put together an enhanced M4A1 using LMT stuff. The EBCG has perfect ejection pattern, and everything runs as I would expect. The rifle literally has no recoil
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What is an enhanced m4a1?
What ammo? Barrel length?
MikhailBarracuda91
01-09-20, 04:37
What is an enhanced m4a1?
What ammo? Barrel length?He bought a spm16 and had them cut, crown, and re thread it to 14.5"
We're calling it an enhanced m4a1 because it has an omega rail, EBCG, H2 buffer, white sprinco buffer spring, Magpul sl-s stock, etc
But the actual gun is exactly just a semi auto version of what the product improvement program was for the m4a1
The ammo we used was the Norma tactical .223 from sgammo. It locked open on all 10 mags. We shot 300 rounds that day
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With all the craziness in my life lately, haven't had a chance to follow up with this suggestion that member Vulcan5 PMed me awhile back. It sounds like a good solution to the ebolt extraction issue-
Where can I find the longer roll pins?
He bought a spm16 and had them cut, crown, and re thread it to 14.5"
We're calling it an enhanced m4a1 because it has an omega rail, EBCG, H2 buffer, white sprinco buffer spring, Magpul sl-s stock, etc
But the actual gun is exactly just a semi auto version of what the product improvement program was for the m4a1
The ammo we used was the Norma tactical .223 from sgammo. It locked open on all 10 mags. We shot 300 rounds that day
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I was looking at this ammo yesterday, any thoughts on it? Would you recommend it for training ammo? Do you think its under powered for 223?
Thanks!
Do we have any other reports of how long the extractor springs last? I took apart my bolt and compared the factory springs to some new pairs, and wouldn't you know it, the original springs seem to have quite a bit less tension. I have since replaced them as a precaution, but what I don't know is whether this was a product of wear or they came that way to begin with.
No inconsistent ejection pattern observed with the enhanced bolt or carrier. On a side note, you cannot fit the LMT enhanced extractor springs with the LWRC rubber inserts, there's not enough room.
Do we have any other reports of how long the extractor springs last? I took apart my bolt and compared the factory springs to some new pairs, and wouldn't you know it, the original springs seem to have quite a bit less tension. I have since replaced them as a precaution, but what I don't know is whether this was a product of wear or they came that way to begin with.
No inconsistent ejection pattern observed with the enhanced bolt or carrier. On a side note, you cannot fit the LMT enhanced extractor springs with the LWRC rubber inserts, there's not enough room.
Are you talking about these? Will these work?
https://www.lwrci.com/LWRCI-ACB-Extractor-Spring-Kit_p_29.html
Yes, those are the rubber inserts I was referring to. I have not tried firing the gun with the LWRC springs themselves installed, they may work but I would personally prefer not to increase extractor tension so drastically.
Yes, those are the rubber inserts I was referring to. I have not tried firing the gun with the LWRC springs themselves installed, they may work but I would personally prefer not to increase extractor tension so drastically.
I'm kinda confused because I thought someone on this thread said they used the lwri ones.
To be honest this seems like an overkill for a very expensive bolt which should work thousands, if not 10's of thousands of rounds out of the box. The more reviews and experiences I read about LMT enhanced bolt and BCG the more i'm inclined to think it's not a duty grade product. If I'm not mistaken LMT does not use them in any of their rifles out of the factory.
Inconsistent ejection, extraction, bcg running fast or slow depending on barrel length/port size/buffer weight/etc. Proprietary springs which have issues either out of the box or after a few K rounds, etc. I'm not sure if they are addressing any actual problem with it (vs a milspec bolt) or just selling it based on a marketing alone. Even if they are addressing some of deficiencies in theory, execution seems far from proper for a Tier-1 company.
Compared to a number of BCM/Colt/DD BCGs/Bolts out there vs LMT enhanced it seems like issues constantly come up with LMT even in number count (in percentage terms that would be a few orders of magnitude more). Or is it just seems to me that way?
I've been reading about the EBCG for years and I've always thought they sure caused a lot of trouble and didn't really ever fix anything.
I've been around this site since the beginning and the people here generally seem to tinker and fiddlefart and upgrade things until they don't work.
ETA: Which is not a bad thing as that's how innovation happens.
I'm kinda confused because I thought someone on this thread said they used the lwri ones.Yes, you can put the LWRC 6.8 springs inside the LMT Enhanced bolt. I don't know how well they work but they do fit.
What I was saying was that you cannot take the rubber inserts out of the LWRC springs and put them inside the LMT springs. This was an idea that I previously had in mind.
MikhailBarracuda91
01-28-20, 16:42
I was looking at this ammo yesterday, any thoughts on it? Would you recommend it for training ammo? Do you think its under powered for 223?
Thanks!It's actually the same velocity as 5.56 so I assume it's a similar pressure. Either way this stuff is extremely accurate for the price holy cow!
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kalieracer
02-02-20, 22:16
6k if memory serves me and they are a different spec as to the amount of tension. Here are all the part numbers for a refresh from LMT. I happened to have asked Gene about this just a bit ago, as I was looking to update notes for parts for Gen2 mws bolt refreshes (I have one that is due for service)
(5.56 Enhanced bolt parts)
Extractor – LMP1120 -
Extractor spring – LMP1110B -
Ejector – LMP105 -
Ejector Spring – LMP113 -
Ejector Roll pin – LMP113A -
Do we have any other reports of how long the extractor springs last? I took apart my bolt and compared the factory springs to some new pairs, and wouldn't you know it, the original springs seem to have quite a bit less tension. I have since replaced them as a precaution, but what I don't know is whether this was a product of wear or they came that way to begin with.
No inconsistent ejection pattern observed with the enhanced bolt or carrier. On a side note, you cannot fit the LMT enhanced extractor springs with the LWRC rubber inserts, there's not enough room.
Torquetard
02-12-20, 20:30
This reminds me of when I shot my MRP with a 14.5 carbine length and got seemingly normal ejection, then tried a 16" middy and it was throwing Wolf at 2:30 when the 14.5 had the same throw with m193 (used the same bcg). Is there really any point to having a mid-length as opposed to carbine, if the midlength is more open? The 14.5 would barely cycle steelcase
This reminds me of when I shot my MRP with a 14.5 carbine length and got seemingly normal ejection, then tried a 16" middy and it was throwing Wolf at 2:30 when the 14.5 had the same throw with m193 (used the same bcg). Is there really any point to having a mid-length as opposed to carbine, if the midlength is more open? The 14.5 would barely cycle steelcase
This is a question I've really been asking lately. Like the last 6-7 years.
I've been shooting my Colts alongside some of the best mids and even a couple of intermediates and I'm not seeing the soft shooting like what the original mids did 10+ years ago.
In fact, my 6920s are softer than most.
This reminds me of when I shot my MRP with a 14.5 carbine length and got seemingly normal ejection, then tried a 16" middy and it was throwing Wolf at 2:30 when the 14.5 had the same throw with m193 (used the same bcg). Is there really any point to having a mid-length as opposed to carbine, if the midlength is more open? The 14.5 would barely cycle steelcase
I'm not an expert in AR gas system function, so this is just my basic understanding:
If a carbine length and mid length have the same ejection pattern, the mid length is actually receiving less gas. The bolt is moving at similar speeds because the extraction process with the midlength robs less energy; therefore, less of the force from the gas is used on just unlocking the bolt and pulling the casing out, and more of it can be used to accelerate the carrier.
If you give them both an equal amount of gas, then the midlength's BCG may travel faster. However, you still see decreased stresses and strains during extraction with the mid, so the recoil would probably not be worse. On the upside, you reduce bolt wear during unlocking (which I imagine is more severe than the wear when it locks and goes into battery faster) and increase reliability.
So, in your case, the 16" mid and 14.5" could have been receiving similar amounts of gas with correspondingly similar recoil, but the difference is that the mid would reliably cycle a wider range of ammo under worse conditions.
In effect, a midlength might achieve the same reliability with less recoil, or moderately improved reliability with slightly less recoil, or significantly better reliability with the same recoil. (Up to a point anyway, at some level you run into reliability problems from excessive carrier speed but this requires some rather severe overgassing to my knowledge.)
People talk reliability like it's a fact. It's academic at best.
I've been shooting mids for over a decade, and carbines, 16" carbines mostly, for 20 years and over my bazillion rounds I've never been able to deduce any reliability difference between the two.
The few problems I've had have magazine and gas tube/BCG related.
This reminds me of when I shot my MRP with a 14.5 carbine length and got seemingly normal ejection, then tried a 16" middy and it was throwing Wolf at 2:30 when the 14.5 had the same throw with m193 (used the same bcg). Is there really any point to having a mid-length as opposed to carbine, if the midlength is more open? The 14.5 would barely cycle steelcase
Ejection pattern is influenced by too many variables to give any useful information.
This is a question I've really been asking lately. Like the last 6-7 years.
I've been shooting my Colts alongside some of the best mids and even a couple of intermediates and I'm not seeing the soft shooting like what the original mids did 10+ years ago.
In fact, my 6920s are softer than most.
Buffers play a large role in how recoil feels. The recoil of a properly gassed middy with a carbine weight buffer will have harsher recoil than a carbine gassed AR with an H2 buffer.
Buffers play a large role in how recoil feels. The recoil of a properly gassed middy with a carbine weight buffer will have harsher recoil than a carbine gassed AR with an H2 buffer.
No. The lighter the reciprocating mass, the lighter the recoil.
All the heavy buffer stuff being smoother/lighter is only applicable to severely overgassed barrels. Which are apparently en vogue here these days.
No. The lighter the reciprocating mass, the lighter the recoil.
All the heavy buffer stuff being smoother/lighter is only applicable to severely overgassed barrels. Which are apparently en vogue here these days.
Negative. The lighter the reciprocating mass, the less recoil transferred to that mass, assuming the same speeds.
Do not make the mistake of equating harsher recoil with more recoil or softer recoil with less recoil. During testing of carbine, H & H2 buffers, I found the carbine buffer to have sharper felt recoil than the H buffer and the H buffer gave sharper felt recoil than the H2. I assume this is the result of quicker acceleration/deceleration of the lighter reciprocating mass.
I would like to point out that during these tests it took the same amount of gas for full function with the carbine buffer as it did with the H2 buffer.
You started out comparing a properly gassed mid/Car buffer to a carbine/H2 and said the mid would be harsher.
It wouldn't because the carrier speed would presumably be slower with less weight than the carbine.
You started out comparing a properly gassed mid/Car buffer to a carbine/H2 and said the mid would be harsher.
It wouldn't because the carrier speed would presumably be slower with less weight than the carbine.
My 16 inch middy with a carbine weight buffer had harsher recoil than my 14.5 carbine gas with an H2 buffer. I assume it's because the lighter mass accelerates quicker, just like lightening a car lets it accelerate quicker.
That's a product of the gas port.
If your barrel wasn't pushing the BCG so hard it would absolutely be softer with a carbine vs a heavier buffer.
That's a product of the gas port.
If your barrel wasn't pushing the BCG so hard it would absolutely be softer with a carbine vs a heavier buffer.
I will say this for the last time- Testing a properly gassed AR shows it has softer recoil using an H2 buffer than it does using a carbine buffer.
Testing an over-gassed AR shows it has softer recoil using an H2 buffer than it does using a carbine buffer.
Regardless of gas system length.
Ok. That's why I don't think overgassed is proper. Less weight moving = less felt recoil/sight disturbance/whatever. Because the gas drive is reduced to keep the the carrier velocity down, not adding weight behind it.
Ok. That's why I don't think overgassed is proper. Less weight moving = less felt recoil/sight disturbance/whatever. Because the gas drive is reduced to keep the the carrier velocity down, not adding weight behind it.
You are correct. Over gassed is over gassed and a heavier buffer will not fix it.
The same goes for buffers. A buffer that's too light is to light and attempting to undergas the AR wil not fix it.
When I tested the carbine, H & H2 buffers, all three needed the same gas setting for full function. When the gas was set for full function with the H2 buffer, that was the gas setting needed for the carbine buffer. When the gas was closed one click, the AR short stroked with the carbine buffer. The difference was that the lighter buffer gave sharper recoil.
If you want softer recoil with a lighter buffer, you'll need to use lower pressure ammo.
Sparky5019
04-08-20, 15:53
Im tracking.
IF this is the case, does anyone say, Wolf, make a stronger extractor spring? Are the dual extractor springs simply milspec springs or are they proprietary? I haven't taken it apart to look as im on duty for a few more days so I figured I would ask here.
For a mil-spec bolt I use the Sprinco ejector springs. To my knowledge they’re about the most high-speed springs you can get.
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