This is one of the best posts I've seen on this subject and is worth repeating here. It was posted by Iowagan on the RugerForum.net:
"Well, everyone has their own opinion so I'll take the other side. Here's the basic requirements of self defence as related to bullets:
1. The bullet must be accurate enough to hit what you are aiming at.
2. The bullet must function and feed reliably in your gun.
3. The bullet must create a large wound channel.
4. The bullet must penetrate far enough to inflict great bodily harm.
5. The bullet should not overpenetrate.
Let's look at theses one at a time.
1. Most guns will be equally accurate with either a FMJ or JHP. Dead heat.
2. Most guns feed more reliably with FMJ than any other type of bullets. FMJ wins.
3. A FMJ will create a large wound channel, often more terminal than a JHP. Reason: Tests done by the Government and independent labs prove a JHP will not "open up" reliably until velocities of 1000 fps are achieved. That rules out all 45 ACP factory JHPs except 185 gr bullets. Typical velocities for a 230 gr is 850 fps. 925 fps for a 200 gr and 1000 fps for a 185 gr JHP. Actually, on human flesh, there is very little difference in wound channels between a FMJ or JHP. Yes, JHPs do open up nicely on a wet phone book but I've never seen a wet phone book attack. Dead heat.
4. A 230 gr FMJ rates at the top of the list for proper penetration. A 230 gr FMJ will penetrate through winter clothing, a JHP that opens up probably won't. Depth of a wound is just as important as diameter of a wound. the 230 gr FMJ wins, hands down.
5. A 230 gr FMJ seldom punches through a "center mass" hit and even if it did, the bullet would not have enough energy left to do much damage. If a JHP does open up, it will "under penetrate" and not make a deep enough wound channel. If it doesn't open up, it will be no different than a FMJ. Believe it or not, this is pretty much a dead heat with a slight edge to FMJ.
Guess which bullets are in my 45 ACP Commander?
Now if you are talking about a lighter 9mm bullet driven to 1200 fps, then the opposite is true in 2-5 above as RNettles posted. This is exactly why the military and law enforcement made such a big mistake going with the 9mm cartridge. The diameter, weight, and velocity of a 45 ACP FMJ bullet makes it one of the all time best self defense, police, and military cartridges ever designed. Maybe that's why a the 45 ACP has passed the test of time for 96 years. Granted, the 9mm has been around just as long but has a poor reputation for wound channel and over penetration. Some think the magazine capacity makes a 9mm better. The studies say different. A typical 45 ACP 230 gr FMJ has an 85% chance of a one shot center mass knock down. Two shots increase the odds to 95%. A 9mm 115gr FMJ has a 45% chance of a 1 shot knock down and only a 70% chance with two shots. If you do the math, the 45's 8 round capacity has a much higher odds of knocking down multiple "targets" than a 9mm with 16 round capacity. Now when you change to a JHP in a 9mm, the performance increases to a 60% chance with a one round center mass hit and 80% with two round hits. Now the odds would be about even with a 9mm high capacity magazine.
These numbers aren't mine or something I just made up. They are well documented by military and other Government agencies as a result of lengthy studies by the US Dept of Justice. I used to work there."
