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9mm vs .45 ACP

9mm vs .45 ACP

Posted by 80-Lower.com on May 21st 2021

It's an age-old argument: 9mm vs .45 ACP. Which one is better? Is there a "better" cartridge between the two, universally speaking? There's less than one-tenth of an inch of difference (0.095", to be exact) between the two bullets' diameters. 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, that it's more accurate and provides more capacity to boot. But are these the only arguments to be made? Are any of them even true? (Spoilers: no) Let's review and lay this to bed.

9mm Summary

The 9mm cartridge has become arguably the most popular handgun round today. Virtually every handgun manufacturer produces a bulk of their pistols to chamber the Parabellum/Luger cartridge, and its high power, small size, and reliable accuracy make it an excellent, well-rounded caliber for sidearms and pistol-caliber carbines like the AR9.

Specs & Measurements

  • 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
  • Grain weights: 90 grains to 185 grains

.45 ACP Summary

The .45 ACP has been around for about as long as 9mm, and has provided military units with an even more powerful cartridge that boasts high stopping power and utter reliability. Since its original chambering in the M1911, the .45 ACP has become a popular carbine round. Many shooters favor it over 9mm for its advertised ballistic specs and sheer size. It can also be suppressed easily without sacrificing performance, thanks to its slow and heavy profile.

Specs & Measurements

  • 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
  • Grain weights: 78 grains to 250 grains

Specifications Compared

Just how physically different are 9mm and .45 APC? Obviously, the .45 is wider by about 27% but produces much lower pressure. About 40% less, to be exact. Although .45's case capacity is almost exactly 50% greater, 9mm produces approximately 60% more pressure. Overall lengths are substantially similar, which is why you'll find many handgun and carbine platforms that chamber both loads with little change to the firearm's length, size, or components. Importantly, both calibers provide similar and often identical grain weights.

How does all this translate into ballistic performance downrange? Can 9mm hit harder than .45 and can .45 run faster than 9mm? Let's take a look at a spread of cartridges from each caliber to find out.

Ballistics Compared

We can't collect data for every load that 9mm and .45 come available with. That would require a short book on its own. However, we can compare the most popular loads for each. For 9mm, we're comparing data for 115-grain to 124-grain loads and for .45 ACP, we're comparing 145-grain to 230-grain load data. We're including +P ammunition in these comparisons to be as thorough as possible.

Muzzle Velocity


  • 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 APC

  • 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


  • 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 APC

  • 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.

Velocity and Energy Compared

Averaging out 9mm's loads, we get a velocity of around 1,230 FPS. If we average out the speeds of .45's common loads, we get a velocity of about 1,060 FPS. Overall, 9mm tends to run about 16% faster. 9mm's average muzzle energy registers at 400 lb-ft. The average energy of .45 ACP comes in at 465 lb-ft. Overall, .45 hits 16% harder, constituting a nearly perfect tradeoff of speed and power between the two cartridges. But it's important to note that if you step away from common commercial ammo and invest in some purpose-designed cartridges for either load, you'll find these two cartridges can easily out-shoot each other when it comes to velocity and energy.

.45 Can Still Outrun 9mm

We looked at average variants for both calibers, but that does not mean these two rounds can trade places. Take the 90-grain Performance Plus Platinum available for .45 ACP, and you'll find a muzzle velocity of around 2,036 FPS. 

9mm Can Hit Harder than .45

And if you invest in the 9mm's 185-grain Seismic heavy hitters, you can achieve muzzle energy of over 900 lb-ft with a handgun-length barrel. Chamber it in an AR9, and you'll be slamming some serious energy downrange.

Max Effective Range

The max effective range of either cartridge is difficult to determine. That's because 9mm and .45 no longer reside in simple handgun frames. With rifle-length barrels chambering these rounds, either one is easily capable of providing good accuracy up to 200 meters, with the right loads. 

To instead determine performance downrange, let's compare bullet drop from the muzzle to 100 yards. If either load is fired from a typical 1911 sporting a 5" barrel, a 124-grain 9mm will drop 12", while a 230-grain .45 will drop 16%. The ACP's drop represents a 33% increase over 9mm at 100 yards, and that difference is expected to widen as distance increases. For reference, that same 230-gr. load will drop 12" at around 85 yards from a 5" barrel.

But again, you can effectively out-shoot either cartridge with the other by simply investing in lighter or heavier loads. Although the average .45's max pressure is much lower than 9mm, investing in a light 90- to 110-grain load will allow the ACP to easily mimic the bullet drop of a 9mm at similar distances.

AR9 vs .45 ACP (AR-15) Ballistics

Let's forget about handguns and short barrels for a moment. After all, we're here for AR-15s. How does each cartridge perform when fired from a 16" barrel? Ballistics By The Inch provides the below muzzle velocity data for both loads.

Averaging out our spread of load data, we see 9mm averages a muzzle velocity of around 1,370 FPS at the muzzle of a 16" barrel. For .45, that average is around 1,194 FPS from the same barrel length. Keeping in line with our original percentages above, that means 9mm is around 15 to 16% faster than .45 ACP when fired from a rifle.

Supersonic vs. Subsonic Velocities

If you're in the business of trying to keep your rounds traveling at subsonic speeds (below 1,125 FPS) for the purpose of effective suppression with a silencer, this is where the differences between .45 and 9mm finally begin to show. Any round traveling supersonic won't suppress well, because it's breaking the sound barrier with that classic, echoing "crack" downrange. If you prefer suppressing your pistol-caliber carbine, you'll need to stick with .45 ACP to enjoy good suppressed performance.

Felt Recoil

Another simple argument: The .45 tends to provide about twice as much felt recoil. However, we're talking about felt recoil, and this doesn't just involve raw force and energy. Many shooters remark that the .45's recoil, although overall stronger, gives more of a "push", while 9mm provides more of a "snap". Although this sounds entirely anecdotal and qualitative, it can have a major impact on your ability to shoot, and to even enjoy the firearm you've invested in. It pays to test out both cartridges in both a steel-frame and polyemer-frame handgun before ultimately making your decision.

Which Round is Better? 

If we're focusing solely on performance - speed, accuracy, velocity, bullet weight - the simple answer truly is, neither round is better than the other. Both 9mm and .45 ACP can perform the job of the other. Either load can travel faster or hit harder than the other with the right bullets. The one advantage .45 ACP may have over 9mm is its ability to be more easily suppressed when fired from a rifle, since 9mm has a tough time remaining subsonic with a 16" barrel. But it's not just about raw ballistics. There are hollow-points to consider, and magazine capacity. Let's discuss.

Both Hollow Points Perform Well

The short summary of 9mm vs .45 ACP hollow points is this: They can both expand to toughly 3/4 of an inch and provide devastating wound channels. Will .45 expand ever so slightly more? Yes, to about 0.79", maximum. The typical 9mm JHP will expand to around 0.72". Is less than one-tenth of an inch going to make a difference? No. Absolutely not. 

Magazine capacity

Thanks to modern double-stacked handgun mags and the pistol-caliber carbine/rifle magazine, capacity is no longer a major differentiator when considering 9mm over .45. While most 9mm handguns can hold about 2 to 3 more rounds, it's a simple investment to just buy a longer magazine with a finger mold protruding from underneath the grip. And the difference is entirely inconsequential if you're building or buying any type of 9mm or .45-cal rifle. 

Other Comparisons

We've covered just about every argument that has been made when comparing 9mm and .45. Now it's time to look at the truly most important part of the argument: The firearms these cartridges go in. It may come down to simple availability of a particular handgun or rifle, and personal preference of the firearm itself, that determines whether you pick one cartridge over the other. 

Available Platforms

If you select the 9mm cartridge, you'll gain access to a wider selection of available firearms, especially if you're in the market for a compact or subcompact handgun. The physical differences between these two cartridges may seem minor, but the .45's weight and size creates challenges for manufacturers who wish to chamber it in small frames. 

Of course, the age-old debate between the merits of the Glock and 1911 can be settled: Both platforms provide these two cartridges as available chambers. The 9mm 1911 is a comfortable and very accurate handgun, and the .45 Glock is accurate and handles the extra recoil quite well.

Lastly, if you love AR's and want a pistol-caliber carbine, 9mm will be your best choice. The .45 AR is a niche, custom weapon that simply isn't available on the market, while the 9mm AR is well established and is compatible with most 55.56/.223 AR-15 parts. 

Cost per Round

There's little competition here. The 9mm cartridge is simply cheaper and more readily available. Current prices for 9mm range at around the $0.50-per-round mark, while .45 ACP starts at around $0.70 to $0.75 per round.

Summary: Picking 9mm or .45 ACP

So, can anybody say that, universally, .45 is better than 9mm or vice versa? If you're just making a general statement without a firearm platform or specific use in mind, the answer is no. Period. End of story. 

That's because both cartridges are too similar and can effectively mimic each other when it comes to power and velocity. Even if you're comparing the "average" 9mm to the "average" .45, one is only 15% faster and one is just 15% more energetic. Both rounds' JHPs expand virtually identically and both experience around a foot of drop at 100 yards, give or take a few inches, when fired from a handgun. These are insignificant differences for the average shooter, especially in a self-defense situation.

You can only truly say one's better than the other when it comes to specific needs. The 9mm can, when chambered in a rifle, shooter farther than .45. And .45 can be suppressed with subsonic ballistic performance that is effectively better than 9mm at shorter distances. These instances are the only examples wherein you can argue one cartridge is "better" than the other.

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