The Great Debate: 9mm, .40, or .45?
We examine which of these popular cartridges makes for the best defensive load
There is a huge amount of misinformation out today about the effectiveness of defensive handgun cartridges.
It’s true that new bullets have better terminal performance than older, less-advanced bullets. However, the performance gap between cartridges stays the same. What has changed is that the new bullets have elevated performance levels, so that cartridges that were once considered to be ineffective self-defense rounds are now thought to be acceptable.
However, no matter what you hear, remember this: A bigger, heavier bullet carrying more energy equals higher performance. That’s physics, and the laws of physics are pretty much a fixed set of rules.
Here we’ll look at some ballistic facts about the three primary defensive semiauto pistol calibers in use today—the 9mm, .40 S&W, and .45 ACP—along with the pros and cons of each. It will help you decide which is best for you. I used Barnes TAC-XPD self-defense ammo for the comparisons, and used figures from 9mm +P and .45 ACP +P ammo in order to give the cartridges every advantage possible. +P ammo is loaded to a higher pressure than standard ammo and is more powerful. It’s designed only for modern handguns that are rated for +P ammo only. (The .40 S&W is not +P.)
Scores of modern guns are chambered for it. It’s the handgun caliber of choice for the U.S. Army and for multitudes of concealed carriers. How did this 115-year-old cartridge become the world’s favorite?
- 9mm+P: 115 grains (Velocity: 1125 feet per second)
- .40 S&W: 140 grains (Velocity 1120 feet per second)
- .45 ACP +P: 185 grains (Velocity 1000 feet per second)
Light bullets shed velocity and thus energy faster, both in the air and in the target. Retained energy aids in penetration of the target. With all else being equal, a heavy bullet will always penetrate deeper than a lighter bullet. Obviously, the 115-grain 9mm bullet is the lightest of the three. The .40 has 122 percent more bullet weight than the 9mm, and the .45 has 161 percent more bullet weight than the 9mm.
- 9mm+P 115 grains: .355
- .40 S&W 140 grains: .400
- .45 ACP +P 185 grains: .452
The bigger the bullet, the bigger the hole it makes in the target. The 9mm bullet has the narrowest diameter of the three. The .40 is 113 percent of the diameter of the 9mm, and the .45 bullet is 127 percent of the diameter of the 9mm.
- 9mm+P 115 grains: 323 foot-pounds
- .40 S&W 140 grains: 390 foot-pounds
- .45 ACP +P 185 grains: 411 foot-pounds
As velocity increases, so does energy, but at a much faster rate, which can be a bit deceiving. For example, a light bullet going very fast may have more energy than a heavy bullet at moderate velocity, yet the terminal performance of the heavy bullet may be better.
That said, energy is still a standard by which a cartridge’s performance is measured. The 9mm (in 115-grain +P) has the least energy of the three. The 140-grain .40 S&W has 120 percent of the energy of the 9mm.+P. The 185-grain .45 ACP +P carries 127 percent of the energy of the 9mm+P.
- 9mm+P 115 grains: 18.5 lb-ft/s
- .40 S&W 140 grains: 22.4 lb-ft/s
- .45 ACP +P 185 grains: 26.4 lb-ft/s
Many ballistic experts believe that momentum is a better measure for a bullet because it does not have the velocity bias that energy does, and it gives the weight of the bullet more importance than energy. The 115-grain 9mm+P has the least momentum of the three.
The 140-grain .40 S&W bullet carries 121 percent more momentum than the 9mm +P. The 185-grain .45 ACP+P bullet has 143 percent more momentum than the 9mm +P.
A deadly shootout between bank robbers and FBI agents in Miami led to the development of the cartridge that’s a top choice for personal defense.
What About the .380 ACP?
Perhaps the next in popularity among handgun calibers is the .380 ACP. This cartridge, with an 80-grain bullet going at 990 feet per second, has 174 foot-pounds of energy—which is less than 55 percent of the 9mm +P’s 317 foot-pounds of energy.
The 9mm is thought by many experts to be marginal for serious defensive-carry consideration, but by comparison, the .380 is pretty puny. In the world of muscle cars, it’s a 1987 Yugo. Yes, the new bullets help, but they can’t turn a pipsqueak into a dragon slayer.
You still need the horsepower pushing on them to make the bullets work.
When people purchase a handgun chambered for .380, most buy the gun, not the cartridge. They like the easy concealment and handling of a little pocket pistol. But the 9mm guns are getting nearly as compact, and they carry a lot more wallop—something to consider if you have to shoot a bad guy.
The Bottom Line
Numbers do not lie. The cartridges are not the same. That said, make a choice, but make an informed choice. As for me, I like them all, but gravitate to the biggest, most-powerful cartridge that is practical to have in a defensive-carry pistol. When my life may be on the line, I want all the help I can get.
It was carried by American troops for over a century. Untold numbers of civilians own one. Why is the 1911 the greatest pistol in U.S. history?