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Thread: B&T Rotex Print-X mystery----acuraccy completely gone on one rifle, but not another.

  1. #1
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    B&T Rotex Print-X mystery----acuraccy completely gone on one rifle, but not another.

    I have a B&T Rotex Print X 556. I also have a surefire RC3. I have one gun that absolutely HATES the Rotex. I mean, insane, trash groups.

    On myColt EPR 11.5… It will shoot nice groups w/55 or 77 at 00. Consistent POA/POI. If I put the Rotex can on it the groups go TOTALLY INSANE. OK, so it must be the can. However, If I swap on my RC3 the gun goes right back to shooting Consistent POA/POI.


    However, my OLD Colt commando upper I have been shooting for 10 years and has 8k plus rounds through it. If I shoot it with RC3 It is good but it also shoots nicely with the Rotex. Obviously, the zero shifts since the Print-x is way bigger but it shoots consistent groups, tight groups.
    SO WTF? Both guns have the exact same surefire FH. Obviously, the one on my Old upper is beat to shit, but it is the same part.

    Why would the rotex open up the groups like crazy on on 11.5 and not on other. Any possible solution? And let me be clear. I am saying 55 grain PMC will shoot a 5 shot group inside a fist when shooting casually with either rifle with the RC3. But the Rotex opens up the groups to completely inconsistent on the EPR. I am talking about pizza box sized stuff you wouldn't accept on a counter-bored mosin you pulled out of a pond.

    The only thing I can think of is some sort of interaction between the B&T surefire mount and the newer FH on my EPR. But I can't figure it out.

  2. #2
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    I would inspect the Rotex for any signs of baffle strikes or endcap strikes. Check bore alignment with a suitable reaction rod or one ordered from McMasters in the correct sizing. If bore alignment is off, I'd remove the muzzle device and reinspect the shims/etc used to install it.

    I've never seen that kind of accuracy loss from a suppressor unless a baffle or endcap strike was involved.

  3. #3
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    Yeah, there’s no end cap strike. Or baffle strike. And more confusing if I put it on my other colt, accuracy is as expected. Weirdest damn thing I’ve ever seen

  4. #4
    Site Supporter farscott's Avatar
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    The issue sounds like the barrel vibration problem that Browning solved with the BOSS. As a round is fired, the forces imparted into the barrel cause the barrel to oscillate. Those oscillations have both a natural frequency and an amplitude. By adding a weight at the end, the amplitude and frequency of the oscillation at the muzzle are impacted. By allowing the weight to move very slightly along the muzzle, lengthening or shortening the barrel, the amplitude, the amount of movement at the muzzle, can be changed.

    In practice, the BOSS is basically a micrometer screw bored out for bullet passage. By screwing the BOSS in and out and moving the weight along the barrel axis, a shooter could find the sweet spot where the muzzle position is consistent for a given load when the bullet exits the barrel.

    https://www.browning.com/support/faq...SH10qGC0iq-F8D

    To solve the OP's issue, either the suppressor has to be moved slightly along the barrel axis (not really a good or practical idea) or some weight needs to be added or taken away from the barrel and/or suppressor. Without high-speed video, this is very much a hit-or-miss "try and try again" situation. If possible, I woiuld consider changing accessories mounted to the barrel or taping fishing weights on the can to see if one can luck onto a sweet spot to tighten the groups.

  5. #5
    What muzzle device/adapter are you using to attach on these rifles? If it's an A2 then the question is whether it's attached using a crush washer. If so, the alignment may be off just enough to where it's not causing baffle strikes but perhaps disturbing the bullet before it departs.

  6. #6
    Site Supporter HeavyDuty's Avatar
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    This is a common event with SIG MPX, too - the 4.5” barrel seems particularly affected. Some people get a shotgun when they mount a suppressor, some don’t. I seem to be lucky with my two. The common wisdom is that it’s a harmonic issue.
    Ken

    BBI: ...”you better not forget the safe word because shit's about to get weird”...
    revchuck38: ...”mo' ammo is mo' betta' unless you're swimming or on fire.”

  7. #7
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    Quote Originally Posted by Greg Bell View Post
    Yeah, there’s no end cap strike. Or baffle strike. And more confusing if I put it on my other colt, accuracy is as expected. Weirdest damn thing I’ve ever seen
    Did you check suppressor bore alignment, or not? [MENTION=23692]RealSelf[/MENTION] made a great suggestion about the A2 muzzle device. If you're using the B&T A2 HUB adapter, and your A2 device was installed with crush washers like a normal USGI item instead of being installed with shims to get proper alignment, that can cause all sorts of issues. You can't use crush washers to mount a muzzle device that's used to mount a suppressor.

  8. #8
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    Quote Originally Posted by JRB View Post
    Did you check suppressor bore alignment, or not? [MENTION=23692]RealSelf[/MENTION] made a great suggestion about the A2 muzzle device. If you're using the B&T A2 HUB adapter, and your A2 device was installed with crush washers like a normal USGI item instead of being installed with shims to get proper alignment, that can cause all sorts of issues. You can't use crush washers to mount a muzzle device that's used to mount a suppressor.
    It is a Surefire FH and adapter. Alignment is good on Rotex and RC3

  9. #9
    Quote Originally Posted by Greg Bell View Post
    It is a Surefire FH and adapter. Alignment is good on Rotex and RC3
    And how is that flash hider mounted exactly?

  10. #10
    Quote Originally Posted by RealSelf View Post
    And how is that flash hider mounted exactly?
    In other words, do you have it properly timed with shims, etc? If it's not properly timed then that may cause issues itself. What is the model of muzzle device on the problem gun?

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