ORIGINAL: cascadedad
Head, sorry to hear about your injury. I hope you are back hunting in no time.
I came to this website primarily to learn, but I can't help jumping in when someone is spouting nonsense. These guys often answer with, "Show your proof!". But they make wild claims and then when they are called on it they can't answer.
Maybe BA can, I don't know. I don't buy into energy being the only factor. Bullet design factors in. Bullet diameter is also a factor. I think the point was already made. Why do LEO's prefer a .40 or .45 over a 9mm?
Somebody please tell me what body armor has to do with any of this?
Bullet design does factor in and I've never said anything that can even be construed as the contrary. That is why I always say that a bullet designed for big game will kill in any caliber be it 7mm, 260 or .338.
Bullet diameter isn't a factor in theory, but mass is. If diameter matteredwe would still be lobbing giant cannon balls instead of pushing very small projectiles very fast.
Look at the 270 WSM. It pushes a 150 gr bullet over 3000 fps and makes more energy than a .308 using a 180 gr bullet.
The 5.7 is .223 caliberand in 40 gr. FMJit can penetrate class III body armor while a 150 gr. 9mm FMJ cannot. So I ask you: whyisn't the bigger bullet better performer?
Because the 5.7 is going 2200 fps out of a pistol and the 9mm is barely making 1000 fps. This causes the 5.7 to make as much energy as a 9mm with a bullet almost1/4ththe mass.
So in answer to your question: the LEO's prefer a .45 over a 9mm because it makes more energy at 50 than a 9mm does at the muzzle! Believe me, if they could get that kind of energy out of a smaller diamter bullet (which they can it's the .357 SIG) then I'm sure they'd be all for getting it.
Why do they prefer the .45 over the .357 mag? The mag makes more energy but it doesn't come in a convient 11 round magazine or compact rapid fire package...until the SIG.
But then you get into the politics of "pet" cartridges etc....
In the kinetic energy equation, velocity is squared where mass is not.
What I haven't touched on is how bullet design transfers that kinetic energy into the target but that is a whole nother discussion.
I'll leave it at this: bigger bullet is not always better. Kinetic energy and transferring that kinetic energy into the target is the king.