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Thread: LMT Enhanced BCG Questions

  1. #1
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    LMT Enhanced BCG Questions

    Recently I tested and compared a recent generation LMT enhanced carrier with the standard carrier in a 16" midlength MRP. The ammunition used was Federal and IMI M193. The only variables during this test were the carrier and a cam pin, and I doubt the cam pin would have changed anything significantly; all other components, including the bolt (an LMT enhanced), remained the same. Buffer tube used was standard carbine, not a VLTOR. The parts were cleaned and fairly well lubricated beforehand.

    The primary difference I noticed was that whereas the rifle previously ejected to about 1:30 with 5.56 ammunition, the gun is now ejecting to approximately 2:15 to 2:30. While not totally bizarre, this was not what I expected, as I had read that the carrier velocity usually increases with the Enhanced carrier. Ejection pattern doesn't tell everything of course but I would assume that a shift backwards in a properly functioning gas system would usually imply slower cycling.

    It seems there are a lot of people on this board who are much more knowledgeable than I on this subject, so I had the following questions:

    1. Is this the usual behavior when installing an enhanced carrier in such a system? I have seen it suggested that the enhanced carrier tends to bleed off more gas with higher powered rounds, whereas with underpowered loads the extended cam pin track helps the gas system accelerate the carrier longer in spite of the extra vent holes. In effect, the Enhanced BCG does a better job of "self-regulating." Certainly other tests with adjustable gas blocks would suggest the latter benefit does exist, but I have found less on whether the EBCG may actually reduce carrier speed with higher pressure loadings.

    2. If indeed the EBCG does reduce carrier speed with full power 5.56 loadings in this gas system, would this reduce reliability with 5.56 pressure cartridges in cold & dirty conditions, since the carrier is getting less momentum in spite of the easier extraction? Or would such inoptimal conditions replicate the effect on an underpowered round to some extent, in that the longer "action time" during lockup would help the carrier move along?

    3. I know that the gas entry hole from the key into the carrier is bifurcated. Is the divider located on the key, or on the carrier itself? I would assume it would be on the carrier itself to maintain parts commonality and for simplicity's sake. Wanted to ask as I had a gunsmith replace the factory key with another, standard mil-spec key. (Factory key had been dented during an unrelated incident, no fault of its own.)

    4. Since the stress and forces involved during extraction are reduced, and the carrier seems to be moving more slowly, would the EBCG be reducing recoil slightly in this instance? I didn't really notice anything significant but it would make logical sense.
    Last edited by LimeSpoon; 12-02-19 at 08:27.

  2. #2
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    It's just a carrier with extra ports to bleed off gas more efficiently. The reduction in pressure is slowing the speed down.

  3. #3
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    Good information here on the LMT Enhanced BCG:
    https://smallarmssolutions.com/home/...d-bolt-carrier

    And this is a helpful video:
    https://www.youtube.com/watch?v=HZkK70Miz60

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    I am running the lmt ebcg in a colt m4 clone with a colt cage code marked m4 (14.5).i can honestly say I feel the slightest difference as compared to the factory bcg(slightly softer recoil impulse).
    I am patiently awaiting the coldest part of the season here in southern ohio to lube it up as normal,with a lite coat of 10w30 Mobil one oil,sit it outside for a few hours and see if she has enough gas pressure to run reliably...
    It has passed all the other tests I can think to try...
    I did order extra extractor springs from lmt,when doing so I answered a silly question about star wars and was rewarded with some serious swag,I only ordered 6$ worth of springs,paid 12$ for shipping,and got 40$-50$ worth of swag...
    Great company!!!
    Last edited by Milspec78; 12-05-19 at 18:45. Reason: Grammwr

  5. #5
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    Quote Originally Posted by Torquetard View Post
    It's just a carrier with extra ports to bleed off gas more efficiently. The reduction in pressure is slowing the speed down.
    Its actually quite a bit more than that. But you summed it up in a nutshell.

  6. #6
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    You would think so, but under some circumstances the longer acceleration time of the carrier outweighs the extra vent ports, and the LMT EBCG actually moves faster than a standard carrier. People with adjustable gas blocks have noted that you can set the port one size down and still get last round BHO.

    What I am interested in is in what conditions the enhanced carrier increases or decreases carrier velocity, and what sort of effect on reliability this has with full power 5.56 loadings.

  7. #7
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    The one LMT enhanced bcg I've been using the most just sheared its second cam pin. Granted, the first one happened eons ago in a different upper, but they seem to have in common 16in barrels and silencers. Different brands, the one thing in common the LMT enhanced bcg.
    Should I make something out of it, or just pure coincidence?

  8. #8
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    Quote Originally Posted by Goldorak View Post
    The one LMT enhanced bcg I've been using the most just sheared its second cam pin. Granted, the first one happened eons ago in a different upper, but they seem to have in common 16in barrels and silencers. Different brands, the one thing in common the LMT enhanced bcg.
    Should I make something out of it, or just pure coincidence?
    "using the most" meaning what? How many rounds? How often? Facts needed.

  9. #9
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    Quote Originally Posted by CAMagnussen View Post
    "using the most" meaning what? How many rounds? How often? Facts needed.
    Yea since mine is going in a suppressed 11.5. Whenever it comes in about 5 months. Lol


    Sent from my iPhone using Tapatalk

  10. #10
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    The first time I noticed it while taking it apart after a four day, approx 2,500 rounds (very give or take) training class, with a dozen or two suppressed.
    Don't keep track of how many rounds I fire. I just open the packages, dump them in the ammo box, and then load mags. But I don't believe it's been more than a thousand rounds until the same thing happened again, with a few mags with silencer. Different upper, lower, cam pin, cans, everything. I could be wrong on the round count, though.
    I'm using other LMT bcgs in suppressed SBRs, but I'm guessing not more than 500 rounds on the one I use regularly at the matches.
    Not jumping to any conclusions, but it looks like the bcg does not deal with over-gassing as well as I would have hoped. This is the only explanation I have.

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