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300 BLK - 9" vs. 12.5"

Discussion in 'Rifle Country' started by ny32182, Jan 3, 2012.

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  1. ny32182

    ny32182 Member

    Oct 17, 2003
    Clemson, SC
    I have been unable to locate a discussion on the exact tradeoffs between these two barrel lengths, other than some subsonic velocity numbers. As expected, there is very little velocity difference between the two with subsonics. What I am curious about:

    -What is the velocity difference with supersonic loads?
    -Is there any notable reliability difference between the two (example: will 12.5" be notably more reliable with subsonics and no suppressor?)
    -Is there likely to be any real difference in suppressor lifespan between the two?

    Has anyone shot significant numbers of rounds through both? Thanks.
  2. C-grunt

    C-grunt Member

    Jun 12, 2005
    Phoenix Az
    I have been looking at similar barrel lengths. From what I have seen the difference in super sonic loads should be about 100-150 FPS. It was specifically designed for the short barrels so you dont see a huge jump in muzzle velocity when you go longer. Not sure on the other questions. I have read though that because the 300 BLK is a lower pressure round that its pretty easy on suppressors.
  3. Z-Michigan

    Z-Michigan Member

    May 19, 2008
    You'll find most 300BLK answers here:


    This exact question was asked there recently, and the expert's reply was that 12.5" supersonics would have a velocity about halfway between the 9" and 16" barrel velocities. (Not a big surprise, but these things don't always work the way that intuition suggests.)

    I don't know about reliability, which will depend mostly on gas port sizing. If you want to maximize can life I would use a brake-style suppressor adapter (like an AAC Brakeout, or most Surefire adapters) and not worry any further.
  4. rsilvers

    rsilvers Member

    Jun 21, 2004
    There is no reliability difference.

    I don't have 12.5 inch velocities, but the 9 and 16 are on Wikipedia.
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