re: FBI 9MM Justification, FBI Training Division

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r. It performs well. But I don't see the purpose of bashing the other 3 calibers (40. 45, 357 sig).

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I never did such a thing. I've always said it's personal preference and that you will get marginal performance differences from any service caliber. Just do your research on the best JHP bullet/barrel length combination for your gun and carry often.

FWIW I carry Hornady Critical Defense. It's a standard pressure, light-for-caliber 9mm. ShootingtheBull's test of it convinced me that it was better out of a short barrel than the Critical Duty I was carrying. I learned that (in basic terms) greater velocity = less penetration using the same cartridge. To put in basic terms, A Critical Duty out of my 3.5" M&P will penetrate MORE than it will out of my 5" Core. Plus, Critical Defense penetrated between 12-13" in his test. That data would lead me to believe that if I had to use my gun in self defense that te bullet may stay in the perp, which is ideally what I would prefer to happen. That was how I came to the conclusion of what to carry.

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That's progress, right Bap?

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I guess it just depends on if you want large bore over capacity. If the difference is around 500 lb-ft for the hottest loads of two different calibers, I will take my chances on my errant/accurate follow-up shots. 500 x 2 > 600.