.45 ACP vs. 9mm:

Back in the day, when servicemen and law enforcement officers carried a lot of M1911 pistols, the .45 Automatic Colt Pistol Cartridge carried the day.

Designed over 100 years ago to beat the performance of its predecessor, which was a smaller .30 caliber cartridge, the .45 ACP fired a larger, heavier bullet that produced formidable stopping power.

Servicemen carrying arms chambered in .45 ACP fought with distinction through two World Wars, but in recent years, it has been heavily eclipsed by the 9mm, a lighter-kicking cartridge that still offers good performance.

So how do these cartridges compare to each other? This post will break down some of the details.

Both the .45 ACP and 9mm Luger cartridge can vary considerably in the weights of the bullets with which they are loaded.

For the former, the .45 ACP is typically loaded with bullets somewhere in the area of 230 grains, although there are some that are loaded with bullets that are heavier. The weight can vary down to as low as 90 grains.

The 9mm Luger is often loaded with bullets that weigh between 115 and 147 grains, although there are loads on either end of this. A 9mm can weigh as little as 50 grains and as much as 185 grains.

As you can see there is some potential for overlap, but since your average .45 ACP bullet weighs more than 200 grains, on the whole .45 ACP cartridges are loaded with heavier bullets. On top of that, the .45 ACP’s bullet is wider and bigger than the 9mm Luger’s.

Since the .45 ACP fires a slower, heavier bullet, muzzle velocities are on average lower for this cartridge. Most are in the neighborhood of around 800 FPS, but they can be as high as 950 and as low as 750 FPS. Typical muzzle energy for the .45 ACP is 350 ft-lbs, but can be higher than 600 ft-lbs.

The 9mm Luger fires its bullet a bit faster, generally around 900 and 1300 FPS, with average loads usually sitting right around 1050 or 1100 FPS. Since the bullets are lighter, the muzzle energy is usually around 300 to 480 ft-lbs, although there is some variance on both sides.

Recoil is primarily affected by the propellant charge and the weight of the bullet, but it is also influenced by the weight of the gun, which you also have to take into account.

With that said, it should be noted that the .45 ACP generally produces considerably more felt recoil than the 9mm. There are things that can be done to mitigate recoil, like installing heavier guide rods or outfitting the platform in question with a muzzle device, but overall the .45 ACP kicks harder.

This is one of the reasons that the .45 ACP was gradually replaced in official duty by the 9mm, since the latter is lighter and produces reasonably comparable stopping power at the cost of lower felt recoil, making it easier for shooters to control.

Both of these are pistol cartridges with big, fat, slow-moving bullets. As a result they have a seriously drooping trajectory with a very limited effective range.

Both are most effective at around 50 yards but can be used effectively at about 100, if the shooter has the requisite skill.

With that said, the 9mm will drop by as much as half an inch at 20 yards, over 3 inches at 50 yards, and more than a foot at 100 yards. The .45 ACP is pretty bad too, dropping more than 4” at 50 yards and more than 15” at 100.

All in all, these are close-range calibers.

It has already been demonstrated that these two cartridges can produce similar stopping power (resulting from the weight of the bullets) but as far as sectional density is concerned, they’re also somewhat fairly matched. It’s also dependent on bullet weight, but 9mm usually exhibits sectional density between .09 and .16, whereas .45 ACP usually has an SD between .13 and.15, giving it a slight edge most of the time.

While there is a lot you can learn from a ballistic comparison of .45 ACP vs. 9mm ammo, it is important to recognize that in terms of how the bullet will be used, the bullet type is one of the most important factors.

For instance, for optimal penetration, a full metal jacket bullet is best; for energy transfer, a hollow point bullet that expands rapidly is best. This is an important distinction when attempting to determine which is the best .45 ACP ammo or best 9mm ammo for a given application.

What’s the Best 9mm Ammo? What’s the Best .45 ACP Ammo?

Ultimately, what the best 9mm ammo or the best .45 ACP ammo comes down to the one that performs best for your specific purpose.

For target practice and training, full metal jacket (FMJ) rounds are ideal. While many believe lighter bullets like 115gr 9mm have less recoil than heavier ones like 147gr, velocity is the key factor. If both have the same velocity, the lighter bullet will have less recoil. However, heavier bullets often have lower velocities, resulting in less felt recoil. The same principle applies to .45 ACP or most other handgun calibers.

For personal defense, hollow point or bonded rounds are preferred. These are designed to expand upon impact, offering superior ballistic performance compared to FMJ. Common 9mm defensive rounds are typically 124gr or 147gr, and they tend to perform ballistically better than the lower grain weights.

Kiesler Police Supply has been a proud official supplier of Speer, Federal Premium, Remington, and CCI ammunition to law enforcement agencies around the country for more than 50 years. If you have more detailed questions about .45 ACP vs. 9mm ammo, please contact one of our representatives and we would be more than happy to help.