(U.S. Navy photo by Journalist Seaman Apprentice Marc Rockwell-Pate)

When the United States military switched from the legendary M1911 to the M9 Beretta, a lot of hell was raised, to put it mildly. The M1911 had served with American troops for nearly three-quarters of a century and it fired a .45 ACP round that had a reputation for stopping enemy troops. The 9x19mm NATO round the M9 fired was... well, not quite so potent, at least in the minds of many.

The thing is, the 9x19mm NATO is not a bad round. It fires a 124-grain full metal jacket bullet at 1,150 feet per second, producing 364 foot-pounds of energy. By comparison, the .45 ACP round sends a 230-grain full metal jacket bullet at 835 feet per second, generating 356 foot-pounds of energy.

In short, you don't want to be hit by either round — but the 9x19mm NATO is more lethal than many would have you believe.


Metrics aside, how have these rounds actually performed? Well, that's the real issue. Being good against ballistic gelatin or a paper target is one thing, but being effective against against the living is something else.

During fighting with the Nazis, an American officer holds the tried-and-true M1911 while fighting alongside a French partisan.

(US Army)

To put this matter to bed, a retired homicide detective from the Detroit area, Evan Marshall, gathered his own data on the effectiveness of different types of ammo. He computed how often a given round was able to achieve a "one-shot stop" when hitting an enemy's torso. In his 2001 book, Stopping Power: A Practical Analysis of the Latest Handgun Ammunition, Marshall and Edwin Sanow defined a "stop" as when an aggressor collapsed before being able to carry out another aggressive act.

The M9 has served for over 30 years, but was derided by those who liked the .45 ACP punch of the M1911

(USMC photo by Lance Cpl. Todd Michalek)

His work allows us to compare the .45 ACP of the much-beloved M1911 with 9mm rounds, like the ones fired by the less-popular M9.

The legendary .45 ACP achieved a one-shot stop 62 percent of the time. That's not bad — almost five-eighths of the time. Marshall did not have data for the 124-grain NATO round, but he did have data for a very similar 115-grain full metal jacket round in 9mm. This round achieved one-shot stops 70 percent of the time — even better.

The choice of 9mm rounds for the M17 wasn't controversial — largely because the M9 proved very capable over three decades of service.

(US Army)

In short, the 9mm seems to hold its own when compared to the .45 ACP. Additionally, given that the M9 (which had a 15-round magazine) and the M17 (which has a 17-round magazine) both hold far more rounds than the M1911 (seven rounds in the magazine), it arguably gives a grunt greater firepower and a better chance of stopping the bad guy.