9mm vs. 45 ACP – What’s The Difference? Which One is Better?
Travis Olander 06.14.23
It’s an age-old argument: 9mm vs .45 ACP. Which one is better? Is there a “better” cartridge? Lovers of .45 ACP say there are few other rounds capable of providing the same type of “Mac Truck” stopping power. Lovers of 9mm say it’s one of the most versatile handgun rounds ever made. And, of course, it provides more capacity to boot. But are these the only two arguments to be made? Let’s review and lay this to bed.
9mm Parabellum at a Glance
The 9mm Parabellum (or 9mm “Luger” cartridge, as it was originally called by Georg Luger in 1902) has long been the submachine gun and handgun cartridge of choice for the Army, Navy, Air Force, Marines, law enforcement, and plenty of NATO and non-NATO forces globally.
It’s seen service for more than three decades in the Beretta M9 and M9A1 alone, and thanks to its century-long life, the 9mm has been optimized beyond just about any other handgun round. Some loads provide supersonic travel for long-range accuracy, while many more provide reliable subsonic speed and accuracy, making the 9mm perfect for suppressed fired.
The Quick n’ Dirty on .45 ACP
The .45 Auto, or .45 ACP (Automatic Colt Pistol), cartridge is, like the 9mm, a century-old military cartridge designed by the legendary John Browning in 1904. It first saw service in the U.S. Army’s M1911 handgun, and it remains in service with certain Army and Marine units today.
9mm vs 45 ACP: Specs Compared
Let’s break down each round’s physical specifications and then talk about performance:
- 9mm
- Bullet diameter: 0.355″ (9.01 mm)
- Neck diameter: 0.380″ (9.65 mm)
- Base diameter: 0.391″ (9.93 mm)
- Rim diameter: 0.392″ (9.96 mm)
- Rim thickness: 0.050″ (1.27 mm)
- Case length: 0.754″ (19.15 mm)
- Overall length: 1.169″ (29.69 mm)
- Case capacity: 13.3 gr H2O
- Max Pressure (SAAMI): 35,000 PSI
- 45 ACP
- Bullet diameter: 0.452″ (11.5 mm)
- Neck diameter: 0.473″ (12.0 mm)
- Base diameter: 0.476″ (12.1 mm)
- Rim diameter: 0.480″ (12.2 mm)
- Rim thickness: 0.049″ (1.2 mm)
- Case length: 0.898″ (22.8 mm)
- Overall length: 1.275″ (32.4 mm)
- Case capacity: 26.7 gr H2O
- Max Pressure (SAAMI): 21,000 PSI
So, 9mm and .45 ACP are similar in total length, but that’s where the similarities end: The ACP cartridge is 9% longer, yet it produces 40% less chamber pressure than the 9mm cartridge. Yet it does this with a case capacity that’s 50% greater. Comparatively, 9mm is a thin, fast round that burns its powder rapidly. The .45 ACP is a wide, slow round that wedges through the air and whatever’s standing in its way. Speaking of speed and power, let’s see how these physical specs translate into ballistic terms.
9mm vs 45 ACP: Ballistics
It’s important to remember these two cartridges are available with varying grain weights. To make a comparison that’s relevant to the common shooter, we’ve selected these two rounds’ most popular grain weights: For 9mm, we’re listing data for 115-grain to 124-grain loads and for .45 ACP, we’re listing 145-grain to 230-grain load data. We’re including +P ammunition, too.
Muzzle Velocity
- 9mm
- 115-gr Federal FMJ: 1,180 FPS
- 124-gr Federal FMJ: 1,150 FPS
- 124-gr Underwood FMJ +P: 1,225 FPS
- 115-gr Winchester JHP +P: 1,335 FPS
- 124-gr Cor-Bon JPH +P: 1,250 FPS
- .45 ACP
- 230-gr Winchester FMJ: 835 FPS
- 230-gr Double Tap FMJ: 960 FPS
- 165-gr Hydra-Shock: 1,060 FPS
- 185-gr Underwood JHP: 1,100 FPS
- 145-gr Glaser Cor-Bon +P: 1,350 FPS
Muzzle Energy
- 9mm
- 115-gr Federal FMJ: 335 ft-lbs.
- 124-gr Federal FMJ: 364 ft-lbs.
- 124-gr Underwood FMJ +P: 413 ft-lbs.
- 115-gr Winchester JHP +P: 455 ft-lbs.
- 124-gr Cor-Bon JPH +P: 434 ft lbs.
- .45 ACP
- 230-gr Winchester FMJ: 356 ft-lbs.
- 230-gr Double Tap FMJ: 471 ft-lbs.
- 165-gr Hydra-Shock: 412 ft-lbs.
- 185-gr Underwood JHP: 497 ft-lbs.
- 145-gr Glaser Cor-Bon +P: 587 ft-lbs.
Speed and Power Compared
If we look at the spread of 9mm’s velocities, we arrive at an average velocity of 1,228 FPS. For .45 ACP, we find an average velocity of 1,061 FPS. The speed of sound is 1,125 FPS. Any bullet traveling near or past this speed is supersonic. We can see that all listed 9mm loads are supersonic. All but one of .45 ACP’s loads (the +P) are subsonic.
Only subsonic ammunition can be suppressed effectively. Supersonic rounds are simply louder and suffer from that signature downrange “crack” of breaking the sound barrier after the round exits the muzzle (or suppressor). So, .45 ACP is a more effective cartridge for subsonic, suppressed fire.
If we average out the muzzle energies of all grain weights, we arrive at an average of 400 ft-lbs. of energy at the muzzle for 9mm. For .45 ACP, we arrive at around 465 ft-lbs. of muzzle energy. If we make percentage comparisons, we find that 9mm is approximately 16% faster. But .45 ACP hits approximately 16% harder. It’s a nearly perfect tradeoff, giving up speed for power and vice versa.
Max Effective Range
Trying to figure out the max effective range for either of these cartridges isn’t as simple as it seems. That’s because both 9mm and .45 ACP are popular for pistol-caliber carbines. These rifle-length firearms provide the absolute highest velocity for both cartridges, and either load will be capable of hitting with good accuracy at 150 meters to 200 meters with a 16″ barrel.
If we look at handgun barrel lengths and accuracy (say, both cartridges being fired from a 5″ barreled 1911) we can begin to compare these two loads more consistently with bullet drop. From that barrel, at 100 yards, the typical 124-grain 9mm will drop about 12″, while the typical 230-grain .45 ACP will drop about 16″, or about 33% more.
So, Which is Better?
Comparing ballistic performance, it’s easy to dismiss .45 ACP in favor of 9mm for its straighter, flatter trajectory and higher velocity. Yet .45 ACP provides more power, and for the sake of practical shooting (whether in self-defense or at a range), both rounds will provide similar accuracy at 50 yards or less.
9mm vs. 45 ACP Hollow Points
Expansion and lethality is one hot topic that’s often debated when comparing 9mm and .45 ACP. But the truth is that both loads’ jacketed hollow points provide similar, if not identical, expansion. It’s been found through testing with ballistic gel that .45 ACP tends to expand up to 0.79″ while 9mm tends to expand up to 0.72″. That’s a negligible difference when either round hits its mark: Both will be devastating against a soft target. That’s where the real question comes in: What will you use either cartridge for?
Application Matters
If you’re looking for a hard-hitting, close-range caliber, then .45 ACP will edge out 9mm. If you enjoy suppressors and want to shoot without hearing protection after you slap a can on the muzzle, .45 ACP wins again.
If you’re gunning for maximum accuracy at distance or you prefer a higher magazine capacity, then 9mm will provide better performance. That holds especially true if you’re building a pistol-caliber rifle.
