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Thread: NSWC testing on gas systems. CARBINE VS MID-LENGTH

  1. #31
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    Quote Originally Posted by sinister View Post
    Accuracy starts to degrade quicker on the 7" carbine gas length as the downrange side of the gas port erodes quicker. You're talking a significant port pressure delta in those two inches' difference between 7 and 9 inches.
    I used to have those charts... out of quick load. They'd show the pressure levels throughout the barrel... 3-5k reduction from carbine to mid if I remember right.
    "You people have too much time on your hands." - scottryan

  2. #32
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    Armalite had a very good pressure curve graphic posted on their tech notes. This is a variation (63-grains being close to legacy M855 Green Tip):



  3. #33
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    Quote Originally Posted by ABNAK View Post
    That MIGHT, maybe, be the only answer that makes sense. i.e. it's CHF vs non-CHF. Maybe......

    EDIT: *might* affect accuracy but not velocity.

    Wonder who made the CHF barrels for this test?
    If you have a projectile that enters the rifling at an non optimal angle due to a less than concentric chamber, muzzle velocity won’t be affected but downrange performance of that ever so slightly deformed round with an ever so slight oblong movement to its spiral rotation will show degraded accuracy and probably velocity.

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