Originally Posted by timdog
I agree on the 45 over the 9, but disagree on a 45 penetrating more deeply because of it's mass. The 9mm (true with the 40sw as well) has more speed and less mass/size, meaning less frictioned surface and as a result can pass through a body with a greater chance of not being impeded. A 45 being bigger has a better chance of hitting hard bone and the surface of the round slows it down very quickly. It is also a sub 1000fps bullet, where the 9 and 40 exceed that.
I have a 45 for BG's and a 9 for more range shooting (9's ost about 5-8 cents a round cheaper off the internet).
You kind of missed the point. Penetration is a product of mass and velocity. Velocity is lost very quickly in a body. An FMJ bullet will not lose mass (not much at least). The mass is more important than velocity (within reason). A .45 has a far better chance of preaking through bone than a 9. That is why really big game hunters use large, heavy, non-expanding bullets at relatively low velocity for tough thick skinned game like Cape Buffalo. You do not hear about African hunters using .300 Weatherby's with steel core bullets for rhinos.
Don't get me wrong. I have a 9mm and have no hesitation carrying it. Good bullets (Gold Dots) properly placed are very effective. I no longer carry my .45. It is a bit large for what I need and only holds 8+1. I feel more comfortable with 14+1 of .40. 9mm's have more failures to stop than any other LE sidearms (maybe .38spl is up there but that was before decent bullets were invented). FMJ's in a 9mm are notorious for punching small holes in people that do little damage. 9mm's (even in HP form) can and do ricochet off bone. .45's tend to punch through bone to the vitals underneath.