Dynamic shock index...

Discussion in 'General Firearms Forum' started by bac1023, Jun 10, 2020.

  1. bac1023

    bac1023

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    I’m a numbers and ballistics geek and I just love stuff like this...there’s some bias in the formula, but still cool.

    View: https://m.youtube.com/watch?v=cAW7NWrwotE


    it also doesn’t hurt that I’m amazed at what the FK 7.5 caliber is capable of. He actually sand bags it a bit, as true velocity has been closer to 2100fps.

    It’s a pretty darn devastating round. The FK BRNO pistol holds 16+1 of them and is accurate well past 100 yards to boot.

    There’s from cool footage of the pistol in action also. :supergrin:
     
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  2. GlockerBill

    GlockerBill

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    Interesting. But color me skeptical on the formula. Does not take expansion of a small meplat into account. Obviously favors velocity over weight... which well, just so happens to be what the FK 7.5 is. Formula seem arbitrary to me. Math is fine to a point, but I'll take time tested results over an equation any day.
    Still, the FK 7.5 is different enough from the standard 9mm, 40, 45, 10mm world that I will have to check it out. Just what I need after consolidating all my ammo down to the 9mm. Now, if we could just get a plastic striker fired manufacturer to adopt the round!
     

  3. bac1023

    bac1023

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    I hear you

    Formulas aside though, the 7.5 round causes a ton of damage and has shown incredible penetration.

    I’ve seen a lot of kill shots on large game in various videos, plus some other impressive feats of penetration.

    My personal experience is that the round kicks some serious butt. I’ve shot some large water bottles, cinder blocks, and a few other things. Did some long range shooting as well.
     
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  4. bac1023

    bac1023

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    Well BRNO itself has the PSD, which is a polymer pistol and much more affordable than the Field Pistol.

    Not sure it’s coming stateside though.
     
  5. Borg Warner

    Borg Warner

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    I like the 7.5 cartridge But it's too bad that the ammo and components for reloading aren't more affordable and that it isn't chambered in a more affordable gun.

    However, looking at the cartridge dimensions, I see that the basic case is very close to being the same length as the 45 Winchester magnum but the case diameter is smaller than the 45 Magnum but larger than the 10mm. Therfore a wildcat cartridge could be created that duplicates 7.5 BRNO ballistics but in a more affordable gun, like a Glock 21 or 41.

    And since what FK is calling 7.5mm is actually 7.65 or 31 caliber, either 7.5 or 7.65 bullets would work just as well, such as the Gold dot bullets made for teh 327 Federal. And since the 45 Winchester case is fatter, the cartridge could be made shorter and still have the case cpacity of the 7.5 BRNO and be able to feed from G21 and G41 magazines.

    Bullet diameter: 7.8 mm (0.31 in)
    Case length: 27 mm (1.1 in)
    Neck diameter: 8.5 mm (0.33 in)
    Shoulder diameter: 10.8 mm (0.43 in)
    Base diameter: 10.8 mm (0.43 in)

    Bullet diameter: .452 in (11.5 mm)
    Case length: 1.198 in (30.4 mm)
    Neck diameter: .473 in (12.0 mm)
    Base diameter: .476 in (12.1 mm)
     
  6. vikingsoftpaw

    vikingsoftpaw DEPLORABLE ME!

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    I haven't heard this stuff in over 20 years. Take his calibers and velocity data then apply them in Taylor Knock Out Factor.

    Fun with numbers...

    All of this stuff was in vogue before ballistic gel.
     
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  7. CAcop

    CAcop

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    I really miss the IWBA. Doc Roberts is about all we have left of legit wound ballistics.
     
  8. bac1023

    bac1023

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    The FK round really excels in ballistic gel tests also. Very, very impressive performance
     
  9. ironhead7544

    ironhead7544

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    Using the formula, I calculated a rating of 40.392 for the 30 Carbine. This was with a Speer Varminter 110 gr bullet at 1980 fps. I used .150 for the meplat as the picture in the Speer manual looks to be about 1/2 the diameter of the bullet.

    meplat .340 x 1500 x .245 = 124.95 300 gr 44 Magnum at 1500 fps, .245 BC.
    meplat .340 x 1000 x .245 = 83.8 300 gr 44 Magnum at 1250 fps, .245 BC.
     
    Last edited: Jun 12, 2020