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20 in vs 26 inch barrel 308

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    #46
    Stan. I’d focus real hard on reloading techniques. Going transonic isn’t a big deal unless you have stability issues. At that point the bullet can start tumbling then you’re done. Focus on bullet run out. Consistent neck tension. That’ll be the deal breaker in your set up

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      #47
      Originally posted by howabouttheiris View Post
      The bullet will not start to slow in the barrel until the bullet velocity approaches the gas outflow velocity.

      Longer barrels will make the round go faster. (by less for every inch, but still faster)
      Remembered this thread when I watched this video...


      [ame="https://www.youtube.com/watch?v=XCqa2umL8ME"]Cutting The World's Longest Rifle To Find The Perfect Barrel Length - YouTube[/ame]

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        #48
        Cheat sheet ... vs watching long video.

        Sent from my SM-G970U using Tapatalk

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          #49
          Todd Hartnett(clunk. Sound of a name dropping) says a 20" barrel on a 308 will be plenty.

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            #50
            Originally posted by howabouttheiris View Post
            The bullet will not start to slow in the barrel until the bullet velocity approaches the gas outflow velocity.

            Longer barrels will make the round go faster. (by less for every inch, but still faster)

            Using my 6.5 data that I have in the GRT software and playing with the barrel length, a 20" barrel is slower than a 30" barrel is slower than a 40" barrel... and this continues until you get to something that is not practical to be manufactured.

            For f/tr, the max length is dictated by the weight limit for the rifle.
            This is correct.

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              #51
              Originally posted by Drycreek3189 View Post
              So…..a metallic cartridge is like a rocket ? A computer model won’t convince me. Rebarrel a rifle with a 40” barrel and start cutting and chronographing. That will convince me.
              It's not like a rocket, lol..But the expansion velocity of the gas pressure generated by the powder is still greater than the velocity of the bullet. However, really long barrels with small capacity cartridges would reach zero gain much quicker. .22 long rifle won't gain much in a barrel over 16 inches.

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