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Muzzle Velocity listed on the Box

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    Muzzle Velocity listed on the Box

    Are they accurate?

    I'm curious for 2 reasons.
    1) Set up my Ballistic Calculator app
    2) Researching minimum expansion velocity.

    I've been trying out the Hornady 165 grain GMX in my new AR10.
    It's says 2610 for on the box.
    I was looking at an article on Chuck Hawks website from 2009. It started that 2700 fps at the target gives the best expansion. I'm not even turning that at the muzzle.
    My furthest shots been about 100 yds. It was on a pig, in the shoulder. Got a pass through and it looked like a small hole in and a small hole out.
    Same with another pig I shot about 75 yds and 3 Raccoons.
    They all died so the bullet did its job.
    I like the shoulder shot and small exit cause it doesn't ruin much meat.

    My concern is if it'll still work (kill) past 200 yds....

    #2
    The gmx reliably expands above 2000fps according to hornady, which should get you out to about 300 yards. If you want to shoot further than that I would look at bullets of softer metal that expand reliably above 1600fps. The hardness of the metal used for the gmx bullet is why you don’t see much expansion out the back side of the animal.

    The velocity on the box is a good starting point, but is probably shot with a 24” barrel and tour AR10 is probably no more than 20”, so you will have lower muzzle velocity. The only way to really know what the bullet is doing out of your gun is to shoot through a chronograph then use that number in a ballistic software.

    With that 308 I’d just sight in 2” high at 100 yards and be minute of deer to 250 and not worry about dialing and checking the chart. If you want to start shooting at 500-600 or farther, then I’d start messing with ballistic charts.

    Comment


      #3
      Plug 2500 FPS into the calculator to start... Gas guns are typically a little slower, and as spoken about above barrel probably a little shorter than 24 inch test barrel

      look up "Max Point Blank Range" I think close zero is like 36 yards? I'd have to pull up the calculator to verify that though

      Comment


        #4
        What is on the box is a very rough estimate and often over stated.

        Barrel length plays a big role in actual velocity but so do other things. It is very common for 2 rifles chambered the same with same length barrels shooting same loads to have significantly different velocities.

        Comment


          #5
          Originally posted by bboswell View Post
          What is on the box is a very rough estimate and often over stated.

          Barrel length plays a big role in actual velocity but so do other things. It is very common for 2 rifles chambered the same with same length barrels shooting same loads to have significantly different velocities.


          Typically Test velocities are shot under ideal condition and mostly in 26” Test barrels for high velocity rifle cartridges.

          I wish the manufacturers would list on the box what they shot that Bullet through to attain the box velocities; truth in advertising if you will.

          As to your expansion concerns, the All copper type bullets like to be driven at higher velocities to expand reliably. You may consider using the SST or the interbond Bullet instead.


          Sent from my iPhone using Tapatalk Pro

          Comment


            #6
            Originally posted by Mike D View Post
            Typically Test velocities are shot under ideal condition and mostly in 26” Test barrels for high velocity rifle cartridges.

            I wish the manufacturers would list on the box what they shot that Bullet through to attain the box velocities; truth in advertising if you will.

            As to your expansion concerns, the All copper type bullets like to be driven at higher velocities to expand reliably. You may consider using the SST or the interbond Bullet instead.


            Sent from my iPhone using Tapatalk Pro
            I've been considering trying the Hornady Inter Lock and the Browning BCX rounds

            Comment


              #7
              A decent ballistics app will allow you to true the velocity. Plug in your estimate. Box velocity will likely be based on a 24” barrel. Add or subtract 25 FPS per inch should get you close. Get a good 100 yard zero then dial what the app tells you to for an extended range, 3-400 yards and shoot it. Get a good group and see where it compares to the app data. Then plug in the difference in the frying section and it will calculate what your actual velocity theoretically is. My 6.5 measured 2695 avg over a chrono but I was consistently high at farther ranges. Tried the truing and it showed the velocity to be closer to 2730. After I did that I am spot on all the way to 1100.

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