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Thread: Vertical Stringing when Suppressed

  1. #1
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    Vertical Stringing when Suppressed

    “Rifle A” is a BCM 9” 300BLK factory Upper on a BCM factory lower with A5H3 buffer. Muzzle device is a Surefire Warcomp (open tines), and suppressor is a Surefire 300SPS. At 40 meters it is shooting 6-12” vertically strung groups while suppressed. Unsuppressed it groups fine. I shoot Barnes 110gr Tac-TX factory ammo.
    Round Count: 62.

    “Rifle B” is an exact clone of “Rifle A” complete with its own suppressor (the suppressors serial numbers are sequential). “Rifle B” has always grouped well both suppressed and unsuppressed.
    Round Count: 28

    To hopefully keep matters clear we will say “Can 1” lives on “Rifle A” and “Can 2” lives on “Rifle B”


    Day 1:
    Vertical stringing occurred on “Rifle A” with “Can 1” shooting suppressed at 40M. Group size was large (couldn’t measure as half the shots were off the paper of a smaller sized target). I assumed the optic was at fault and checked rings and fit and even tried it on a different rifle. Optic grouped fine and was not the culprit.

    Day 2:
    Vertical stringing occurred on “Rifle A” with “Can 1” shooting suppressed at 40M. Group size was roughly 12”. I then removed the can and shot unsuppressed. Group size was roughly 1”. I suspected the suppressor might not be concentric to the bore but could not visually determine anything wrong or off.

    M4C- 2018-10-05.jpg

    I decided to test swapping suppressors between rifles.

    Day 3:
    Vertical stringing occurred on “Rifle A” with “Can 2” shooting suppressed at 40M. Group size was roughly 6”.

    Vertical stringing DIDN'T occur on “Rifle B” with “Can 1” shooting suppressed at 40M. Group size was roughly 1.5”.

    M4C- 2018-10-13.jpg

    This tells me the suppressors aren’t to blame. This leads me to think that there is an issue with the muzzle device, which I self-installed without a torque wrench. I installed the Warcomps on both “Rifle A” and “Rifle B” on the same day, back to back. Rocksett was used. I didn’t muscle them super tight, just firm enough to time them correctly, but I leave the possibility open that it may be torqued over the specified 20-30 ft lbs. If both rifles had this type of stringing I would be more inclined to believe it was due to over torquing. I could be wrong though.

    What should my next course of action be? I’m nervous about potential baffle strikes so before I experiment further I’m going to inquire with Surefire but thought I’d pose the question here too.

    Break loose the Warcomp and re install to spec? (I assume I would need new shims?) This would be hoping I didn’t mess up the threads/shoulder/bore if I did indeed over torque.

    Check concentricity of barrel to threads? This doesn’t sound like something one can easily do at home. Can a good gunsmith? I admittedly know very little about this topic. Any thoughts are appreciated.

  2. #2
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    Vertical Stringing when Suppressed

    Have you thought about swapping muzzle devices? It seems that’s one of the last things you haven’t swapped between the good Rifle B and bad Rifle A

    Did you time the FH? Does the instructions call for timing the flash hider? I’m thinking they do, but I don’t own that specific FH/can.


    That’s sure a strange occurrence I have never seen with any of my builds.

    And there’s no noticeable difference between rounds of Rifle A suppressed? No difference in recoil impulse or anything along those lines?

    I’d probably start a dialogue with SF and BCM. Just to get this on their radar.

    Good luck man .


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    Last edited by RobertTheTexan; 10-16-18 at 03:31.
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  3. #3
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    Are you getting baffle strikes? Have you checked?
    When looking down the bore, can on, does it look centered?

  4. #4
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    I had a (16") factory, .300 Blk from BCM that shot 5" groups- no suppressor.
    It was verified inaccurate by BCM and exchanged.

    A long shot- have you verified no part (gas block/barrel/etc.) is coming in contact with rail?
    On a bolt gun vertical stringing is usually a bedding issue.
    Last edited by gaijin; 10-16-18 at 06:33.

  5. #5
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    Are you shooting prone?


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  6. #6
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    Quote Originally Posted by RobertTheTexan View Post
    Have you thought about swapping muzzle devices? It seems that’s one of the last things you haven’t swapped between the good Rifle B and bad Rifle A

    Did you time the FH? Does the instructions call for timing the flash hider? I’m thinking they do, but I don’t own that specific FH/can.


    That’s sure a strange occurrence I have never seen with any of my builds.

    And there’s no noticeable difference between rounds of Rifle A suppressed? No difference in recoil impulse or anything along those lines?

    I’d probably start a dialogue with SF and BCM. Just to get this on their radar.

    Good luck man .


    Sent from my iPhone using Tapatalk
    First off, congrats on member of the year! Well deserved.

    I had thought of swapping muzzle devices, but with "Rifle B" being zeroed and my deer rifle for the upcoming rifle season, I'm a little reluctant to do this until after the season.

    The FH is timed correctly on both rifles. And no, no noticeable difference between any of the rounds fired. No different recoil impulses, weird sounds or anything.


    Quote Originally Posted by MegademiC View Post
    Are you getting baffle strikes? Have you checked?
    When looking down the bore, can on, does it look centered?
    No baffle strikes as far as I can tell. Looking down the bore it looks as centered as best as i can see with my naked eye.


    Quote Originally Posted by gaijin View Post
    I had a (16") factory, .300 Blk from BCM that shot 5" groups- no suppressor.
    It was verified inaccurate by BCM and exchanged.

    A long shot- have you verified no part (gas block/barrel/etc.) is coming in contact with rail?
    On a bolt gun vertical stringing is usually a bedding issue.
    There is no contact between any part of the barrel or gas block and the rail.


    Quote Originally Posted by scooter22 View Post
    Are you shooting prone?


    Sent from my iPhone using Tapatalk
    Yes, all shots were prone from the same semi-supported position.

  7. #7
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    @Randall thank you!
    PM sent.

    Might want to ping BCM.


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  8. #8
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    Were these cold bore or after shooting a while? Could be harmonic changes due to the suppressor weight but that shouldn't happen.

    Seems like your right on button with the next step being to take the muzzle device off, clean up everything and see if that changes it. Look at the crown and the muzzle device when you have it off.

  9. #9
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    Occurs both with a cold bore and after shooting a while. I thought about harmonics but with 6-12" groups at 40 meters I kind of discounted that being the sole issue.

  10. #10
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    I hate to suggest anything as I know so little so feel to mock my theory. But it seems too early to me to rule out the cans exacerbating the effect.. If the barrel nut is sufficiently loose might not the extra weight out front be causing an oscillation? If so I would expect some, but less stringing without the can. I didn’t see where the op shot with no can.
    “Madness is rare in individuals – but in groups, parties, nations, and ages it is the rule.” – Friedrich Nietzsche

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