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Thread: Diagnosing Deflection marks

  1. #21
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    Tedfs,

    Did you state any known difference between the two groups of cases shown in the first pic?

    Were they fired out of different uppers or with different charges?
    Or were they just picked up from the same pile and you noticed two different patterns?
    Black River Tactical
    BRT OPTIMUM HFCL Barrels - Hammer Forged Chrome Lined 11.5", 12.5", 14.5"
    BRT OPTIMUM Barrels - 16" MPR, 14.5" MPC, 12.5" MRC, 11.5" CQB, 9" PDW
    BRT EZTUNE Preset Gas Tubes - CAR and MID
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  2. #22
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    All cases shown with the high mark were shot from the Mega upper.
    The others were shot with the BCM upper, which does not have the Tubbs spring but also has lower deflector geometry than the Mega.

    All cases had the same charge and projectile.

    Just trying to diagnose if it's the different geometry of the Mega deflector, too much spring and buffer or a combination of either.

  3. #23
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    Do you have two lowers or just the one with tubbs/H2 buffer?
    If you did, You can try swapping them.

    Both uppers have identical barrels, firing the same ammo.

    Looking at cases to create/diagnose the problem may not be helpful.

    The feel of the rifle cycling should tell you something.
    Look for how far cases fly and in what direction.
    Check for lockback on the last round using a weak grip and weak ammo.
    Then correlate the cases with all that other data.

    The clearly different mega deflector is most likely the single largest factor.

    If both uppers otherwise operate fine, I would not worry about case marks.
    Black River Tactical
    BRT OPTIMUM HFCL Barrels - Hammer Forged Chrome Lined 11.5", 12.5", 14.5"
    BRT OPTIMUM Barrels - 16" MPR, 14.5" MPC, 12.5" MRC, 11.5" CQB, 9" PDW
    BRT EZTUNE Preset Gas Tubes - CAR and MID
    BRT Covert Comps 7.62, 5.56, 6X, 9mm
    BRT MarkBlue Gas Tubes - BRT EXT, EXC and PDW Lengths
    BRT MicroPin Gas Blocks - .750" & .625"
    BRT MicroTUNE Adjustable Gas Blocks
    BRT CustomTUNE Gas Ports

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