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Thread: LMT Enhanced Carrier + A5 system + BCM 14.5" middy

  1. #21
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    Quote Originally Posted by 2 Horse View Post
    Yes on the Vltor spring. I was thinking that all of them were way over gassed until I came across this thread. Now I'm stumped as to what is going on.
    Well, I would agree that your setups are over-gassed to one degree or another (even though your BCM is a BCM, any 16" carbine gas barrel is gonna have way too much dwell time).

    In my search for "reciprocal smoothness", there is no replacement for getting the gas port further away from the chamber while reducing barrel length in front of the gas port. With that said, you can take the concept too far.

    I think this is why Wes at MSTN is currently experimenting with a 17" barrel running a rifle-length gas system (13"). His personal gun is set-up like this now and he's reporting 100% reliability so far.

    There's no substitute for reducing gas port pressure. The LMT carrier has no effect on the pressure at the gas port, but it does affect the amount of time that the expansion chamber inside the carrier is pressurized. The increased length of the cam-pin track also allows the carrier to move slightly further to the rear before bolt unlocking begins (allowing chamber pressure to subside as well). These are all good things.

    But, since the LMT Enhanced carrier design is substantially different from the original Stoner design, there is no guarantee that it will work in a given gun....one simply has to experiment. This is a complex equation; exact chamber dimensions (even within NATO tolerances), gas port placement and diameter, buffer weight, buffer spring compression strength and rate, etc. I won't even pretend to completely understand all the math....I revert to the guess-and-check method.

  2. #22
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    I'm thinking of adding an adjustable gas tube to dial the pressure down a bit. Just don't know how well they hold up.

    The only other choice is to drill and tap the A2 sight, like the JP bolt on one.

  3. #23
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    Quote Originally Posted by 2 Horse View Post
    I'm thinking of adding an adjustable gas tube to dial the pressure down a bit. Just don't know how well they hold up.

    The only other choice is to drill and tap the A2 sight, like the JP bolt on one.
    Get a Syrac block. They are bullet proof. I've got quite a few rounds on my 3 and they're doing great. No chance of adjusting without YOUR intervention.

  4. #24
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    Quote Originally Posted by Brahmzy View Post
    Get a Syrac block. They are bullet proof. I've got quite a few rounds on my 3 and they're doing great. No chance of adjusting without YOUR intervention.
    Have a A2 front sight, so a block is a no go.

  5. #25
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    Quote Originally Posted by 2 Horse View Post
    Have a A2 front sight, so a block is a no go.
    Ah, oops - I failed to read/retain your above post.

  6. #26
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    Quote Originally Posted by Brahmzy View Post
    Get a Syrac block. They are bullet proof. I've got quite a few rounds on my 3 and they're doing great. No chance of adjusting without YOUR intervention.
    If Syrac made a full mil-spec-equivalent adjustable FSB with their mechanism...I would strongly consider it.

    I'm also interested to know if Syrac is using a Chrome Silicon spring for their detent. If the detent spring fails, the mechanism becomes less reliable....CS is much more resistant to heat than most other spring materials.

  7. #27
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    UPDATE:

    I ran 40 rounds of Remington UMC 55gr fmj .223 (white/green box from walmart) and 20 rounds of Wolf mil classic. Locked back on empty using a PMAG and a first gen Lancer L5 30rd (not AWM).

    Tested for lock-back without a shoulder purchase (held only by pistol grip).

    No lube added.

    It's so soft, it feels like the buffer assembly isn't hitting the end of the RE during the recoil stroke. Yet, it still functioned 100% so far.

    Environmental Note: I live in Central Florida (Orlando Metro area) and it's quite hot here. I can't call it GTG till the humidity drops below 99% and the temps drop into the 30's......so ultimate confirmation for me will be a few months.

  8. #28
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    There was some cat using that Syrac block during the Magpul class in Tucson back in April. From what I can remember he had issues with getting his set up running.



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  9. #29
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    Quote Originally Posted by BufordTJustice View Post
    If Syrac made a full mil-spec-equivalent adjustable FSB with their mechanism...I would strongly consider it.

    I'm also interested to know if Syrac is using a Chrome Silicon spring for their detent. If the detent spring fails, the mechanism becomes less reliable....CS is much more resistant to heat than most other spring materials.
    I am running SYRAC. It is great IMHO. if the detent fails to hold the screw in place, then the GB reverts to a normal GB and all if fine.

    https://www.m4carbine.net/showthread.php?t=110249



    C4
    Last edited by C4IGrant; 08-07-12 at 13:10.

  10. #30
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    Quote Originally Posted by C4IGrant View Post
    I am running SYRAC. It is great IMHO. if the detent fails to hold the screw in place, then the GB reverts to a normal GB and all if fine.

    https://www.m4carbine.net/showthread.php?t=110249



    C4
    Grant,

    Great thread. If the SYRAC becomes just as functional as a normal GB upon the screw backing out....it becomes infinitely more attractive to me.

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