As my Sig line will tell you...
...I own all kinds of guns in different calibers, and at the moment I'm going through a revolver infatuation... so I'm not just blindly biased towards .357 Sig (anymore
). I own both barrels for my Sig Pro, so I actually have experience firing both rounds from the exact same gun. These are just my honest thoughts on the subject. I didn't read the entire thread before posting, so I doubt I'll say anything that hasn't already been said 20 times... but, here goes.
My .40 barrel is lonely... I never take it out anymore. There's nothing the .40 can do that the .357 Sig can't do better and faster, IMO. It is bigger, but not by enough to make me feel that it's a better round. If I want bigger I get the .45's out.
Shooting .40 to me just feels like '9mm snap' mixed with '.45 torque.' It has snap, but it also pushes my hands upwards a bit, which makes for longer time between follow-up shots. .357Sig is more snappy with a lot less torque. The .357Sig snaps
straight back very quickly, bringing me back on target faster. It comes back at you with a little authority, but it's manageable.
.357Sig is loud as hell... it has a lot of flash...
That's just a side benefit though
.357Sig was designed to replicate the performance of the .357 Magnum 125gr. load - probably the most successful one-shot-stop pistol round of all time. The .40 is a good size, and moves fast enough that it will drop most bad guys, but it's hardly replicating .357 Magnum ballistics.
.357Sig penetrates barriers (like car doors, automobile glass, etc.) better than .40S&W. This is why LEO's and departments around the country are starting to adopt the round as well.
I am more accurate with .357Sig.
.357 Sig costs me $13-$15 for a 50-box. A tad more expensive than .40, but once again not enough worth mentioning IMO, considering .40 is running $11-$12 per 50-rnd box. It's not hard to find either, if you have a Wal-Mart or sports store within driving distance. It's been a while since I've been somewhere that didn't carry .357Sig.
I know people who have bought .40 caliber guns, and didn't like them.
I've never met, or heard of anyone who owns a .357Sig and doesn't love it. Most of us who own them, love them and have nothing but praise for the round.
9mm = 9x19. IIRC, .357Sig uses a 9x21mm bullet... Don't hang anyone on that info, I could be dead wrong.
Now for overpenetration: I've never worried about overpenetration in any application. It's not a .50BMG - you're not going to kill someone a mile away if the bullet goes through the bad guy, which it probably won't. In the event that it does, I doubt you'll be mugged, robbed, or assaulted in such a crowded public place that bystanders are in danger of catching your rounds after they pass thru the BG. People who want to victimize you usually don't like big crowds.
If you're using JHP's, as most of us do, then don't even worry about it. I had an ND using some really hot .38Spl+P, and because of the room I was in and where I was, I basically ended up firing into my wall through a mirror at point blank range. The bullet hit a 2x4, knocked a chunk out of it the size of a quarter and lodged in the plywood about 5" back... This is from a gun w/a 4" barrel, once again at point blank range - the wall couldn't have been 2 ft. from the muzzle. It did NOT go through the wall... the bullet expanded, and it was so clogged with drywall that I doubt it could have gone through the other side if it still had enough velocity to keep going.
If the same bullet had traveled through a human body and clothing first, I doubt it would have done anything more than break the mirror and land on the floor.
Overpenetration makes 2 bleeding holes, instead of one... which incapacitates the bad guy faster. That's a good thing.
Underpenetration can get you killed. Obviously not such a good thing.
I'm sure the condition of your drywall would be the last thing on your mind after an SD shooting.
