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9mm performance with barrel length

Seen at arfcom, a chart that shows how 9mm AR-15 velocity in feet per second changes by barrel length (thanks to Randall Rausch at

7 Responses to “9mm performance with barrel length”

  1. Marc Says:

    Nice, thanks for the pointer.

  2. Standard Mischief Says:

    That’s pretty neat. I wonder how whoever got all those data points. I suppose it was done with one of those strain gauge thingys. Look to see the initial pressure rise. Although it still does not explain how they know the bullet’s velocity when it is at the 8 mark in a 16 barrel.

    I had initially assumed that someone took a barrel and a hacksaw and recrowned the barrel at 16, 14, 12, 10, 8…. inches, but that’s clearly not the case.

    I’d love to see a bunch of charts showing pistol rounds in various carbine and wheelguns (where the bullet and the driving gases need to jump the gap).

  3. ben Says:

    Strange thing is that the plots seem to be approaching asymptotic values which would clearly be wrong. Eventually, as the length increases, the friction in the barrel will be greater than the force of the remaining pressure on the bullet, at which point the speed should drop. I’d like to see data out past that point as a sanity check.

  4. SayUncle Says:

    Ben, I doubt you’ll see a 60 inch AR barrel.

  5. Mike Lorrey Says:

    Um, isn’t the AR-15 a .223 caliber rifle?

  6. SayUncle Says:

    It’s usually a 5.56 nato. It also comes in many other calibers.

  7. Randall Says:

    The plot above is a Quickload prediction.
    It’s not strain gauge or chrongraph data.

    More info on the Quickload internal ballistics software can be found on

    Randall Rausch

Remember, I do this to entertain me, not you.

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