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Kimber Montana Barrel Cut - Velocity Reduction

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  • Kimber Montana Barrel Cut - Velocity Reduction

    Does anyone have data on velocity reduction on chopped Kimber Montana barrels? I have a Kimber Montana 308 with a stock 22" barrel that I am considering cutting down to 18-20". I've been told to expect a reduction of anywhere between 10-60 FPS per-inch, but I'd like to validate this with real world data if possible. The rifle is currently shooting 150g TSX at 2900 FPS.

    I recognize there are many different theories and points of view as to why I should or should not chop my barrel, and I am not interested in starting a debate on barrel length. I am only looking for input from those with actual experience and data from chopped Kimber Montana barrels.

    Thanks for the input!

  • #2
    For 308, figure between 25 and 50 fps per inch, depending on the powder.
    "Lay in the weeds and wait, and when you get your chance to say something, say something good."
    Merle Haggard

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    • #3
      Call Kimber.
      Their adirondack .308 has an 18" barrel, they may have insights. It's essentially the same as the montana otherwise.

      Curious as to why you are desiring the cut...
      Proud to be an American!

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      • #4
        The only way to know for sure for your gun and your loads is to cut it and chrono it. Generally for bottle neck rifle chamberings with barrels 18" or longer you can expect 25-30 fps/inch loss, cut it shorter than 18" and expect 50 fps/inch loss. So I'd expect your load to run ~2850 fps in a 20" barrel and ~2800 in an 18" barrel.
        Those that are successful in Alaska are those who are flexible, and allow the reality of life in Alaska to shape their dreams, vs. trying to force their dreams on the reality of Alaska.

        If you have a tenuous grasp of reality, Alaska is not for you.

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        • #5
          Cut it to 20" and don't look back. Handiest barrel length in "my" opinion. I currently have a 30-06, 350 rem mag, and 375 Ruger in 20 inch stubs. Enjoy your shortened barrel.
          LIVE TO HUNT....HUNT TO LIVE!!!!

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          • #6
            If you call Kimber make sure the rifles you are comparing have the same twist rate. Slower twist can produce faster velocities than a faster twist. An additional benefit is your barrel will be more ridged after it is cut and may become accurate. What bullets do you hunt with at the moment?

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            • #7
              Just for an example. Click image for larger version

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              • #8
                I sometimes hunt with a .308 Steyr with a 19" barrel. I can easily match the speeds you're getting with the TSX using RL17 hand loads or factory Superperformance ammunition but it really doesn't matter. Neither you nor any critter you might shoot will notice 50fps loss but you will notice how much handier the rifle becomes to carry and pack around.

                Once you go carbine, it's hard to go back.
                "I do not deal in hypotheticals. The world, as it is, is vexing enough..." Col. Stonehill, True Grit

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                • #9
                  Originally posted by fullkurl View Post
                  Call Kimber.
                  Their adirondack .308 has an 18" barrel, they may have insights. It's essentially the same as the montana otherwise.
                  Thanks fullkurl, that's a great idea. I'm bummed I didn't think of that sooner.

                  As far as why I'm considering the barrel cut, I'm really just curious at this point. The Kimber has served me well and has become my go to rifle for everything except for big bear. It's already a light and compact rifle, but if I can cut off a few more inches with minimal velocity reduction, then why not? ~50-75 FPS will not change anything for me.

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                  • #10
                    Originally posted by Kruger View Post
                    If you call Kimber make sure the rifles you are comparing have the same twist rate. Slower twist can produce faster velocities than a faster twist. An additional benefit is your barrel will be more ridged after it is cut and may become accurate. What bullets do you hunt with at the moment?
                    I use 150g Barnes TSX bullets with RL15 powder.

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                    • #11
                      Originally posted by hodgeman View Post
                      I sometimes hunt with a .308 Steyr with a 19" barrel. I can easily match the speeds you're getting with the TSX using RL17 hand loads or factory Superperformance ammunition but it really doesn't matter. Neither you nor any critter you might shoot will notice 50fps loss but you will notice how much handier the rifle becomes to carry and pack around.
                      Thanks hodgeman. Up to now I've just been using RL15 for my 308 loads with great success, but I'll definitely try RL17 (if I can find some) to see how that compares.

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                      • #12
                        Keep in mind you can skin a cat I multiple ways. Hunters down here are killing deer with 300 Blackouts and 6.8 SPC. Consider using the 130gr TTSX. If 2200fps is killing deer and large hogs here then 3000+fps out of your rifle should take care of what your hunting. Just something to think about.

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                        • #13
                          Originally posted by Kruger View Post
                          If you call Kimber make sure the rifles you are comparing have the same twist rate. Slower twist can produce faster velocities than a faster twist. An additional benefit is your barrel will be more ridged after it is cut and may become accurate. What bullets do you hunt with at the moment?
                          All Kimber 84m series .308s are 12 twist, all barrel lengths as well.
                          Proud to be an American!

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                          • #14
                            All good input...but make sure the smith doing the barrel shortening knows how to recrown the muzzle.

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