These are probably three of the most common automatic calibers to carry and I know this isn't the first time someone has asked to compare them. However I was curious as to the foot pound or jules produced by each caliber in the common factory loadings. I have a firearm in each of these calibers. I went to wikipedia... and I'll accept it as a reliable source, at least for an online question and found the following: 9 mm 115 grain FMJ = 570 J and 420 foot pounds pressure. .40 S&W 180 grain FMJ = 598 J and 444 foot pounds. .45 ACP 230 grain FMJ = 561 J and 414 foot pounds. So there really isn't much difference at all in energy expelled from the rounds. I know there's the old saying that speed kills which is why a relatively narrow .30 rifle round can do so much damage with the supersonic speed it produces - three or four times the amount a handgun round. At these lower speeds does the size of the wound channel make the big difference in going with the .45 acp over the 9mm? I ask because if energy is what matters then you would think the 9mm would be a more effective round because it gives off slightly more kinetic energy. I don't know much about ballistics but can anyone explain this or share their thoughts? Wanna kill these ads? We can help!