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Thread: bolt lock back...

  1. #1
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    bolt lock back...

    Issue:

    Bolt will not lock back on last round with suppressor attached. Bolt locks back just fine with no suppressor.

    Factors:

    -Using 55 Grain Privi Partizan 5.56
    -Problem still exists in about 10 different magazines (steel and Pmags)
    -11.5 Bravo Company BFH
    -Fail Zero BCG with BCM Extractor upgrade.
    -Vltor A5 Buffer with -3 Buffer.
    -M4-2000 suppressor and AAC Brake
    -AR Gas Vent Forward Assist

    Any ideas?
    Last edited by pathfinderheli; 05-28-13 at 21:58.

  2. #2
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    It should run in that configuration. I think that gas vent forward assist is part of the issue. My 12.5" has an .076 port and I run an AAC M4-2000. I use the LMT enhanced carrier and -4 buffer.

    Quote Originally Posted by pathfinderheli View Post
    Issue:

    Bolt will not lock back on last round with suppressor attached. Bolt locks back just fine with no suppressor.

    Factors:

    -Using 55 Grain Privi Partizan 5.56
    -Problem still exists in about 10 different magazines (steel and Pmags)
    -11.5 Bravo Company BFH
    -Fail Zero BCG with BCM Extractor upgrade.
    -Vltor A5 Buffer with -3 Buffer.
    -M4-2000 suppressor and AAC Brake
    -AR Gas Vent Forward Assist

    Any ideas?



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  3. #3
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    I would think so as well... That's why I am stumped!

    Can't be a mag thing since I tried numerous ones and it works fine no can...

    Maybe it is the gas vent... Losing too much with the can attached but I would think there would be an issue with no can as well???

  4. #4
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    I think if you put a real one on there it will solve the issue. I also use PPU 5.56.

    Quote Originally Posted by pathfinderheli View Post
    I would think so as well... That's why I am stumped!

    Can't be a mag thing since I tried numerous ones and it works fine no can...

    Maybe it is the gas vent... Losing too much with the can attached but I would think there would be an issue with no can as well???



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  5. #5
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    The only thing I can think of is a overly strongbolt catch spring or BAD lever doesn't allow the catch to come up fast enough to keep up with the faster suppressed bolt carrier.

    Try swapping lowers or applying finger pressure to the bottom part of the catch to help it engage.

    Where are cases ejecting suppressed / unsuppressed ?
    Last edited by Clint; 05-29-13 at 10:31. Reason: Strong not weak
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    BRT EZTUNE Preset Gas Tubes - CAR and MID
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    BRT MicroPin Gas Blocks - .750" & .625"
    BRT MicroTUNE Adjustable Gas Blocks
    BRT CustomTUNE Gas Ports

  6. #6
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    Quote Originally Posted by Clint View Post
    The only thing I can think of is a weak bolt catch spring or BAD lever doesn't allow the catch to come up fast enough to keep up with the faster suppressed bolt carrier.

    Try swapping lowers or applying finger pressure to the bottom part of the catch to help it engage.

    Where are cases ejecting suppressed / unsuppressed ?
    No Bad Lever.

    I'll change the bolt catch spring.

    Can't swap lowers... Only have 1 SBR'd!

    1 PM Suppressed.

    3 PM Un-Suppressed.

  7. #7
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    Clint,

    Is it possible that the AR forward assist gas vent and the combination of the Vltor -3 and Springco is too much? I wonder if that thing is allowing too much gas to escape somehow?

    Quote Originally Posted by Clint View Post
    The only thing I can think of is a weak bolt catch spring or BAD lever doesn't allow the catch to come up fast enough to keep up with the faster suppressed bolt carrier.

    Try swapping lowers or applying finger pressure to the bottom part of the catch to help it engage.

    Where are cases ejecting suppressed / unsuppressed ?



    Owner/Instructor at Semper Paratus Arms

    Facebook: https://www.facebook.com/SemperParatusArms/

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    Master Armorer/R&D at SIONICS Weapon Systems- http://sionicsweaponsystems.com

  8. #8
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    Classic excessive bolt speed. The 3 to 1 oclock is telling considering the other symptoms.

    Ditch that goober lever thing at a minimum. And as Clint mentioned... I've had to trim coils off of bolt catch plunger springs that weren't fluffy... too stiff.

    There's so much aftermarket goat screw going on here it's a rubik's cube. Have you tried a standard USGI spring. I'd think the H3 would be enough weight on a BCM port...
    "You people have too much time on your hands." - scottryan

  9. #9
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    I disagree. His SBR is almost identical to mine with the exception of the BCG and the gas vent forward assist. If I put an A5 -3 in my 11.5 it would lock back 100%. I did it when I ran a standard H3 and blue Springco spring also.

    Quote Originally Posted by markm View Post
    Classic excessive bolt speed. The 3 to 1 oclock is telling considering the other symptoms.

    Ditch that goober lever thing at a minimum. And as Clint mentioned... I've had to trim coils off of bolt catch plunger springs that weren't fluffy... too stiff.

    There's so much aftermarket goat screw going on here it's a rubik's cube. Have you tried a standard USGI spring. I'd think the H3 would be enough weight on a BCM port...



    Owner/Instructor at Semper Paratus Arms

    Facebook: https://www.facebook.com/SemperParatusArms/

    Semper Paratus Arms AR15 Armorer Course http://www.semperparatusarms.com/cou...-registration/

    M4C Misc. Training and Course Announcements- http://www.m4carbine.net/forumdisplay.php?f=141

    Master Armorer/R&D at SIONICS Weapon Systems- http://sionicsweaponsystems.com

  10. #10
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    Quote Originally Posted by markm View Post
    Classic excessive bolt speed. The 3 to 1 oclock is telling considering the other symptoms.

    Ditch that goober lever thing at a minimum. And as Clint mentioned... I've had to trim coils off of bolt catch plunger springs that weren't fluffy... too stiff.

    There's so much aftermarket goat screw going on here it's a rubik's cube. Have you tried a standard USGI spring. I'd think the H3 would be enough weight on a BCM port...
    As stated previous... I have no goober lever...

    I'm thinking its the bolt catch spring...

    Going to get rid of the gas vent as well... Seems like all the new CH handles do a great job at keeping the gas out of your face.
    Last edited by pathfinderheli; 05-29-13 at 11:41.

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