View Full Version : Enhanced BCG's
I am aware of these "enhanced" BCG's : LMT, Sure Fire, Geissele and JP Enterprises. Any others? I'm not a Delta/SEAL/RANGER or anything of the sort and I've never broken any of my BCG's. I use Colt and BCM. Just training and competition for me.
Is there any performance/durability/strength reasons that a plain ole' run of the mill shooter such as myself would need any of these enhanced and expensive BCG's ? Like many here I do find more quality than I really need comforting but at 2X the price do I really need one? Anyone running one of these and noticed a positive difference?
Thanks
at 2X the price do I really need one? Anyone running one of these and noticed a positive difference?
Nope. There's some possible benefits for suppressed shooting. But that's more of the cam pin path... not a strength issue.
Ever clean a phosphate and black nitride BCG back to back?
Nope. There's some possible benefits for suppressed shooting. But that's more of the cam pin path... not a strength issue.
I disagree, there are benefits felt with the LMT on over gassed guns unsuppressed. It softens it recoil by bleeding excess gasses.
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ColtSeavers
07-21-20, 19:37
Ever clean a phosphate and black nitride BCG back to back?
I don't believe this is a coating or treatment issue, but rather a design issue. Flared carrier end for anti carrier tilt, enlarged, more, or repositioned gas vents, dual spring extractor, and such.
I don't believe this is a coating or treatment issue, but rather a design issue. Flared carrier end for anti carrier tilt, enlarged, more, or repositioned gas vents, dual spring extractor, and such.
My point is thats the only benefit that he is guaranteed to notice.
ColtSeavers
07-21-20, 20:14
.....
Our philosophy is to start with a properly configured and properly gassed barrel.
Then use standard components for the rest of the system.
I disagree, there are benefits felt with the LMT on over gassed guns unsuppressed. It softens it recoil by bleeding excess gasses.
Thanks all ! Your responses pretty confirmed my thoughts that as long as one sticks to a properly gassed barrel and all other systems are in proper alignment and strength then a enhanced BCG is not needed. I don't shoot supressed, my shortest barrel is 14.5 and I don't have any full auto. My barrels are all Colt so I assume proper gas.
I disagree, there are benefits felt with the LMT on over gassed guns unsuppressed. It softens it recoil by bleeding excess gasses.
I don't think we disagree. An overgassed barrel is similar to a standard gassed barrel with a can. But we tried shooting them back to back and couldn't really tell a difference. Perhaps a shot timer on a full auto gun would take the subjectivity out of it.
Our philosophy is to start with a properly configured and properly gassed barrel.
Then use standard components for the rest of the system.
Totally agree. Treating symptoms is insane. Get the barrel right in the first place.
I disagree, there are benefits felt with the LMT on over gassed guns unsuppressed. It softens it recoil by bleeding excess gasses.
I've experimented with the LMT Enhanced a little. I had two identical rifles with the same Noveske barrels in each. These seemed to be gassed for reliability, but not really over gassed. For me, there is no detectable difference between a mil spec BCG and the Enhanced when shot side to side using identical buffer setups (carbine tube, Sprinco blue with H2). They ran smooth.
However, that doesn't mean that there might not be a noticeable difference when paired with an over gassed barrel, a different gas system, a different dwell time, a different buffer setup, or a can.
Further, it doesn't mean that the LMT Enhanced won't result in a more reliable rifle over the long term because of its design. In fact, I fully expect the LMT Enhanced BCG to result in a slightly more reliable rifle in the long haul. That's why I bought it.
Is it worth it to spend $300+ for a BCG instead of $180? Probably not, unless you are a high round count professional door kicker who routinely engages bad guys with high rates of fire.
That's not me I'm just a civi who appreciates nice equipment that I'll never use to its design potential.
I've experimented with the LMT Enhanced a little. I had two identical rifles with the same Noveske barrels in each. These seemed to be gassed for reliability, but not really over gassed. For me, there is no detectable difference between a mil spec BCG and the Enhanced when shot side to side using identical buffer setups (carbine tube, Sprinco blue with H2). They ran smooth.
That was our unscientific findings. We tried the quick change method on the same upper.... which was silly, but we too noticed nothing different.
I have an M4-clone I built using a Remington Defense SOCOM barrel and an LMT enhanced carrier with a Cryptic Coatings "Mystic Black" bolt. Haven't shot it yet but will keep you posted. From experience the LMT enhanced carrier also slightly reduces fouling in the process of it's camming action and the "Mystic Black" is really slick and cleans up in a heartbeat.
95% of users will notice nothing, 4% will notice but gain nothing in terms of measurable shooting performance, 1% may actually gain something, sometimes. Maybe.
Unscientific WAG, but I'd put some money on it.
There is a ton of brilliance into the LMT enhanced BCG that few will ever appreciate. So many things make it just outstanding, but is it needed for most folks no. It’s kinda like KAC, nobody needs a KAC SR25 mag, but they don’t suck and are over built for most saps slinging lead down range including me. You are not waisting money buying great kit, but most don’t need it.
PB
I don't believe this is a coating or treatment issue, but rather a design issue. Flared carrier end for anti carrier tilt, enlarged, more, or repositioned gas vents, dual spring extractor, and such.
This. In most calibers I have not had any problems with BCGs from PSA, Toolcraft, RRA, Anderson or AIM Surplus. In 7.62x39, I have an LMT enhanced bolt. 7.62x39 bolts are thinner and run thru extractors faster than 5.56. Bought it about 10 years ago for my first build and later put it in my current 16” carbine. Still going strong on a lifetime of steel case and surplus. But I also paid twice what I got a Toolcraft complete 5.56 BCG for just for that LMT 7.62x39bolt.
I guess you have to ask whether a top quality enhanced BCG that costs twice what a Toolcraft BCG is better than two Toolcrafts. I’ve not seen anyone prove which lasts longer. A bolt is a wear item and will eventually break.
I guess you have to ask whether a top quality enhanced BCG that costs twice what a Toolcraft BCG is better than two Toolcrafts. I’ve not seen anyone prove which lasts longer. A bolt is a wear item and will eventually break.
Agree 100%.
It’s all snake oil as far as I’m concerned. The only actual “enhancement” that has been legitimately proven to be beneficial is the KAC bolt & carrier.
It’s all snake oil as far as I’m concerned. The only actual “enhancement” that has been legitimately proven to be beneficial is the KAC bolt & carrier.
Care to elaborate?
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Dr. Bullseye
07-26-20, 13:47
OP, are you trying to fix something that is not broken? If your mil spec part, any part, does not break, why ever fix it on any component?
It’s all snake oil as far as I’m concerned. The only actual “enhancement” that has been legitimately proven to be beneficial is the KAC bolt & carrier.
Bold statement, and honestly quite ignorant. Other than the chrome sand cutter bolt carrier from KAC their standard carrier is just that. Totally milspec.
You seem to have no knowledge of the LMT enhanced carrier (actually enhanced and definitely not snake oil) and enhanced bolt similar to KAC but uses mil spec extension. The LMT is not snake oil.
The Surefire does what it says, but honestly only really offers all its benifits to full auto fire.
If you took some time to search this site and the internet in general I’m sure you could educate yourself and not find yourself making such ignorant statements in the future.
Bold statement, and honestly quite ignorant. Other than the chrome sand cutter bolt carrier from KAC their standard carrier is just that. Totally milspec.
You seem to have no knowledge of the LMT enhanced carrier (actually enhanced and definitely not snake oil) and enhanced bolt similar to KAC but uses mil spec extension. The LMT is not snake oil.
The Surefire does what it says, but honestly only really offers all its benifits to full auto fire.
If you took some time to search this site and the internet in general I’m sure you could educate yourself and not find yourself making such ignorant statements in the future.
No I’m quite familiar with it, I just don’t care. The bolt is beefed up, but not like the KAC, and it does have an altered cam pin track and increased ventilation that may aid in suppressed or over gassed guns, but to me, personally for the cost, if I’m going for anything other than a quality mil spec BCG, I’m getting a KAC. That’s my opinion and it’s worth absolutely nothing.
There is a ton of brilliance into the LMT enhanced BCG that few will ever appreciate. So many things make it just outstanding, but is it needed for most folks no. It’s kinda like KAC, nobody needs a KAC SR25 mag, but they don’t suck and are over built for most saps slinging lead down range including me. You are not waisting money buying great kit, but most don’t need it. PB
Good post. Adding... Sometimes, such enhanced products were developed to address a specific combination of conditions, components, variables for a group of users dealing with a proprietary issue. Later release and other benefits to everyone else is just incidental.
No I’m quite familiar with it, I just don’t care. The bolt is beefed up, but not like the KAC, and it does have an altered cam pin track and increased ventilation that may aid in suppressed or over gassed guns, but to me, personally for the cost, if I’m going for anything other than a quality mil spec BCG, I’m getting a KAC. That’s my opinion and it’s worth absolutely nothing.
I guess I’m just not tracking why you’d come on a public forum and say it’s ‘snake oil’ then retort with its cause you just don’t care? I stand by ignorance being the right term for all of it.
I'm not sold on LMT's "enhanced" bolt either. There is another thread about their "enhanced" bolt peening. Here's mine after ~2,000rds. I've never encountered a regular milspec bolt that did this after that many rounds. The bolt was only used on a LMT 16" and 10.5" MRP barrels. YMMV
63236
Our philosophy is to start with a properly configured and properly gassed barrel.
Then use standard components for the rest of the system.
This should be the norm, but whatever..
BufordTJustice
08-02-20, 01:20
Good post. Adding... Sometimes, such enhanced products were developed to address a specific combination of conditions, components, variables for a group of users dealing with a proprietary issue. Later release and other benefits to everyone else is just incidental.
Correct. And some things, like the bifurcated gas port into toroidal expansion chamber (formed around the bolt tail), the angle of those twin ports as they direct gas from the gas key, the geometries of the cam pin path, and the location/size/countersink beveling of the additional exhaust ports.... some of those things are the fathers of many patents, hundreds of hours of CFD and physical testing, with dozens of iterations.
Very few items on the AR platform fit all use cases. Triggers, buffer weights, barrels, etc.
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BufordTJustice
08-02-20, 01:20
I'm not sold on LMT's "enhanced" bolt either. There is another thread about their "enhanced" bolt peening. Here's mine after ~2,000rds. I've never encountered a regular milspec bolt that did this after that many rounds. The bolt was only used on a LMT 16" and 10.5" MRP barrels. YMMV
63236
Yeah you should probably read that thread in it’s entirety before referring to it.
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OP, are you trying to fix something that is not broken? If your mil spec part, any part, does not break, why ever fix it on any component?
No, just curious about these new and improved BCG's. I don't have money burning a hole in my pocket but I'm willing to pay for quality if there is a real reason to buy it.
No, just curious about these new and improved BCG's. I don't have money burning a hole in my pocket but I'm willing to pay for quality if there is a real reason to buy it.
I think somewhat similarly to you. I sometimes have money burning a hole, but I’m not willing to pay for extra features unless there is a reason to buy it.
For BCG’s, I have only bought Forward Controls Design’s NP3 (nickel teflon) complete recently. One is in a suppressed-only upper that was built to have correct gassing from the get-go, just waiting on the suppressor to clear to put into use. The other is in my Colt CCU upper. I knew both were/would be gassed correctly, so there was no need to go with bonus features; however, a nice treatment that enhances lubriciousness can’t be a negative when combined with quality components.
I’ve also picked up several bolts and components (gas rings, pins, firing pins, cam pin, extractor springs) when they are on good sales. If you don’t have cash burning a hole in your pocket, just get a Centurion/BCM/Sionics/FCD bolt carrier group, then an extra bolt from one of the same companies, then some extra Colt parts (they’re out there). And some lube.
If you want to save money, Toolcraft nitride or even NiB BCG’s will almost always run just fine, and they used to be on sale for as low as $70. But still get some extra parts from known, quality companies. That way, you’ve saved money and have the same extra parts that you should have even with a higher quality company. If the Toolcraft fails, unless it is a dimensional thing with the carrier itself, you can just drop in your spare parts and rock on. Still should end up saving a bit of money.
Yeah you should probably read that thread in it’s entirety before referring to it.
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Yeah, I did
BufordTJustice
08-02-20, 17:08
Yeah, I did
Then you realize, like the rest of us, that you stepped on your d*ck with that last comment?
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Then you realize, like the rest of us, that you stepped on your d*ck with that last comment?
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How so? Tolerance stacking or that my "enhanced" bolt chipped lugs with 2 factory barrels that I ordered and had them specifically headspace them for me.
BufordTJustice
08-02-20, 17:17
How so? Tolerance stacking or that my "enhanced" bolt chipped lugs with 2 factory barrels that I ordered and had them specifically headspace them for me.
You’re an N of 1. Thousands of users without issues.
You’ve done zero diagnostic work. Do you even have field gauges to ensure the headspace work was done properly? Was it done with that exact bolt, or to TDP? What barrel ISN’T a “factory barrel”?? You machining and torquing barrel extensions to blanks and then drilling the gas ports and alignment pins yourself these days?
I could go on.
You need to get your data right.
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I believe Surefire's bolt is based off the improvements that Jim Sullivan has done in his designs. Not sure what benefit of just having the bolt would be without all the other improvements he has done. Civies can't buy those new and improved guns of his anyway. Man I miss the early 80s...
BufordTJustice
08-02-20, 17:35
I believe Surefire's bolt is based off the improvements that Jim Sullivan has done in his designs. Not sure what benefit of just having the bolt would be without all the other improvements he has done. Civies can't buy those new and improved guns of his anyway. Man I miss the early 80s...
Does the SF carrier have an elongated cam pin path?
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I'm not sure, just going off the description on their site.
I bought a Toolcraft DLC BCG some time back (last year or so?). Haven't used it yet but it is among my other 6 complete BCG's I have dipped in EWL and then placed into storage.
You’re an N of 1. Thousands of users without issues.
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Same exact crap the PSA owners say...
BufordTJustice
08-02-20, 19:33
Same exact crap the PSA owners say...
I see you’re new here.
Talking unfounded sh*t about me isn’t the best way to introduce yourself. But it is a way.
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This is what Bill said: way above my pay grade,
Bill Alexander Bill Alexander is offline
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Let us perhaps be a little more precise with regard to the details of the LMT enhanced bolt and carrier system. As shown the details are very often misinterpreted.
In the first instance one must understand why the system exists, more particulaly in the context that the design is brilliant in its execution, but as reported frequently on the errornet is not always reliable. The design basis for the assembly is specifically to enhance the durability of the M4 configuration as currently issued. This gun is to some extent unbalanced. Port pressures running military grade ammunition are well in excess of the design levels which leads to very high carrier acceleration rates (+22 f/s/s). this combined with chamber pressure drop often creates the undesirable condition that the bolt commences to unlock while still subject to a degree of head thrust from the cartridge case. The result is that the lugs are subject to a biaxial loading of both shear and bending.
The LMT system being both the carrier and the bolt seeks to operate directly in this gun and elleviate symptoms. The carrier is set up with a longer delay during the initial portion of its movement. To facilitate this longer cam path and movement of the bolt forwards in the carrier, the front edge of the carrier is extended such that it still continues to retain the extractor pivot pin. Additional exhaust vents act to drop the piston pressure faster and to relieve any blowby at the tail of the bolt.
The bolt itself is of particular interest. The function of the dual spring extractor is frequently misinterpreted as an attempt to add spring force to the extractor claw. Rather it reduces the fatigue that the extractor spring(s) undergo by allowing the use of longer springs with lower K values; the % relative compression during the movement of the extractor is reduced. Remember that additional extractor force is not required now that the carrier is slowing the extraction cycle. The mitigation of stress in the bolt is accomplished in several ways. Material is the least visible change but is important to the design. The traditional Carpenter 158 is abandoned, being replaced by a significantly tougher grade from a different manufacturer. The lugs themselves are generously radiused between lugs and at the rear the diameter is actually reduced to allow a larger transition radius to be machined. The incorrectly identified sand cuts on the lugs are stress relief cuts. These allow any individual lug to elastically deform and give a smoother load over the contact patch. While this type of feature is very difficult to calculate and even more difficult to implement it helps to place the lug in a true shear load rather than amplify the bending moment. As noted the lug opposite the extractor is relieved. This feature prevents the unequal transfer of load to the two opposite lugs but I would argue that the stress relief groove already in place largely accomplishes this purpose. This is a academic quibble so I will bow to LMT in this respect. There is one additional feature that can be found in the bolt, but I am not at liberty to disclose the detail.
When considering wether to use the LMT parts one must consider the weapon. Correctly ported guns will derive little or no benefit from a carrier that is specifically set up to absorb excessive port pressures and some degree of residual case pressure. If not sufficiently gassed the reliability will suffer. This is not a fault of the carrier rather a mistake made in the application so be careful with simple substitutions. The bolt itself is exemplary. If not constrained by a $ value the bolt is a worthy addition to any rifle and will do nothing but enhance the durability of this part of the system.
Bill Alexander
BufordTJustice
08-02-20, 22:13
Thi sis what Bill said: way above my pay grade,
Bill Alexander Bill Alexander is offline
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Let us perhaps be a little more precise with regard to the details of the LMT enhanced bolt and carrier system. As shown the details are very often misinterpreted.
In the first instance one must understand why the system exists, more particulaly in the context that the design is brilliant in its execution, but as reported frequently on the errornet is not always reliable. The design basis for the assembly is specifically to enhance the durability of the M4 configuration as currently issued. This gun is to some extent unbalanced. Port pressures running military grade ammunition are well in excess of the design levels which leads to very high carrier acceleration rates (+22 f/s/s). this combined with chamber pressure drop often creates the undesirable condition that the bolt commences to unlock while still subject to a degree of head thrust from the cartridge case. The result is that the lugs are subject to a biaxial loading of both shear and bending.
The LMT system being both the carrier and the bolt seeks to operate directly in this gun and elleviate symptoms. The carrier is set up with a longer delay during the initial portion of its movement. To facilitate this longer cam path and movement of the bolt forwards in the carrier, the front edge of the carrier is extended such that it still continues to retain the extractor pivot pin. Additional exhaust vents act to drop the piston pressure faster and to relieve any blowby at the tail of the bolt.
The bolt itself is of particular interest. The function of the dual spring extractor is frequently misinterpreted as an attempt to add spring force to the extractor claw. Rather it reduces the fatigue that the extractor spring(s) undergo by allowing the use of longer springs with lower K values; the % relative compression during the movement of the extractor is reduced. Remember that additional extractor force is not required now that the carrier is slowing the extraction cycle. The mitigation of stress in the bolt is accomplished in several ways. Material is the least visible change but is important to the design. The traditional Carpenter 158 is abandoned, being replaced by a significantly tougher grade from a different manufacturer. The lugs themselves are generously radiused between lugs and at the rear the diameter is actually reduced to allow a larger transition radius to be machined. The incorrectly identified sand cuts on the lugs are stress relief cuts. These allow any individual lug to elastically deform and give a smoother load over the contact patch. While this type of feature is very difficult to calculate and even more difficult to implement it helps to place the lug in a true shear load rather than amplify the bending moment. As noted the lug opposite the extractor is relieved. This feature prevents the unequal transfer of load to the two opposite lugs but I would argue that the stress relief groove already in place largely accomplishes this purpose. This is a academic quibble so I will bow to LMT in this respect. There is one additional feature that can be found in the bolt, but I am not at liberty to disclose the detail.
When considering wether to use the LMT parts one must consider the weapon. Correctly ported guns will derive little or no benefit from a carrier that is specifically set up to absorb excessive port pressures and some degree of residual case pressure. If not sufficiently gassed the reliability will suffer. This is not a fault of the carrier rather a mistake made in the application so be careful with simple substitutions. The bolt itself is exemplary. If not constrained by a $ value the bolt is a worthy addition to any rifle and will do nothing but enhance the durability of this part of the system.
Bill Alexander
What does that guy know?
[emoji41][emoji6][emoji106]. I kid I kid.
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The part in bold is important and corresponds with our position that a properly configured and ported barrel needs nothing else but quality mil-spec components to run well.
When considering whether to use the LMT parts one must consider the weapon.
Correctly ported guns will derive little or no benefit from a carrier that is specifically set up to absorb excessive port pressures and some degree of residual case pressure.
If not sufficiently gassed the reliability will suffer.
This is not a fault of the carrier rather a mistake made in the application so be careful with simple substitutions.
Bill Alexander
I own a select fire M4 machine gun that's running a factory Colt 14.5" barrel. I'd say that barrel is overgassed for reliability. It was running quite fast out of the box.
I purchased an LMT enhanced BCG from brownells dropped it in & it's now slowed down and smoothed out it's firing cycle. I have nothing but praise for it.
Now I dropped that same BCG into a properly gassed 16" AR-15 carbine and had failures to extract, hammer follow and a headache.
Like Bill A. mentioned..it has a specific purpose which it excells at.
openbolt
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