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Thread: Hornady says no non monolithic supersonic bullets in MCX 1:5 twist .300blk with can

  1. #11
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    So, here's a new wrinkle:

    Someone on another forum just shared with me a formula for calculating bullet RPM. 12 / twist rate * velocity *60

    Based on what little chrono data I've been able to find on 110gr .300blk, it looks like 1950fps muzzle velocity would be very optimistic on a 6.75" bbl, with something in the 1900-1850 range more likely. According to the formula shared with me (12/5*1950*60), that works out to 280,800 RPM, worst case. The Hornady guy was only worried about RPM above 300,000.

    Was the Hornady guy calculating based on muzzle velocity for a 16" barrel? It looks like it. I've seen 2300 FPS listed as the MV for 110gr V-max. 12/5x2300x60=331,200 That's almost exactly the figure the guy quoted.

    It's looking more and more like the two incidents I've found documented on the internet were caused by first, a specific 125gr all-copper "slotted" HP bullet and second, a frangible bullet (which I've always read should not be used with a suppressor, in any caliber).

  2. #12
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    Here is a link to the Hornady 110gr Vmax 300 black out ammo. 2375 FPS out of a 16" inch barrel. https://www.hornady.com/ammunition/r...gr-v-max-black
    What kind of RPM would I be getting out of my 9 inch 1:5 twist blackout barrel ?
    Last edited by Biggy; 03-14-18 at 02:14.
    "A free people ought not only to be armed and disciplined, but they should have sufficient arms and ammunition to maintain a status of independence from any who might attempt to abuse them, which would include their own government."
    - George Washington

  3. #13
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    Quote Originally Posted by Biggy View Post
    Here is a link to the Hornady 110gr Vmax 300 black out ammo. 2375 FPS out of a 16" inch barrel. https://www.hornady.com/ammunition/r...gr-v-max-black
    What kind of RPM would I be getting out of my 9 inch 1:5 twist blackout barrel ?
    110gr Vmax from a 9" bbl is around 2190 FPS.

    12 / 5 * 2190 * 60 = 315,360 RPM

    2100 FPS gets you down to 302,400.

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