Many shooters argue that the debate over 9mm vs. 45 ACP comes down to magazine capacity versus stopping power. However, this is a very apples-to-oranges approach when comparing these two personal defense rounds.
We’ll take an objective look and compare the ballistics, advantages, and disadvantages of two of the most popular self-defense cartridges in the world.
Load up your favorite Glock 17 magazines with your 9mm ammo of choice – or build a tiny, protective dam using the beavertail grip safety on your 1911 – because you are about to read the most objective 9mm vs 45 ACP caliber debate on the Internet.
Cartridge Spec Differences
| Specification | 9mm | 45 ACP |
|---|---|---|
| Parent Case | 7.65x21mm | Unique Design |
| Bullet Diameter | 0.355" | 0.452" |
| Neck Diameter | 0.380" | 0.473" |
| Base Diameter | 0.391" | 0.476" |
| Case Length | 0.754" | 0.898" |
| Overall Length | 1.169" | 1.275" |
| Case Capacity | 13.3 grains H₂O | 25–27.4 grains H₂O |
| Max Pressure (SAAMI) | 35,000 psi | 21,000 psi |
Is 45 ACP Stronger Than 9mm?
The 45 ACP is undoubtedly the superior cartridge when it comes to kinetic energy transfer. But how is “stopping power” defined? It cannot be quantified so easily, especially since so much of it is determined by shot placement, which is immeasurable. With that in mind, the FBI test protocol is widely accepted as the best assessment of a cartridge’s efficacy for self-defense, which is certainly something akin to stopping power.
For modern 9mm JHP ammo, penetration is around 13-15 inches on average. In contrast, 45 ACP hollow point ammo will typically penetrate to a depth of 12-14 inches. For the most part, both will penetrate the same distance.
One major difference between the 9mm’s .355" diameter bullet and 45 ACP’s .452" JHP is this: their capacity for terminal expansion. In general, a 9mm bullet will expand up to 0.6", effectively doubling in diameter. The 45 ACP bullet also reliably doubles in diameter, although that means it widens until it is nearly 1" around.
In short, the 45 ACP is more likely to inflict a larger permanent wound channel inside the bad guy. That means additional blood hemorrhaging, higher probability of lacerating a vital organ, and an altogether more unpleasant time for the threat.
Since it gouges out a larger permanent wound cavity, transfers more energy to the target, and is (relatively) less inclined to over-penetrate, it’s fair to say that the 45 ACP has more stopping power than a 9mm. Recent advancements in hollow-point technology have significantly improved the 9mm’s performance, although the 45 ACP’s bullet remains the larger and more damaging one.
But this is only part of the story! Let’s continue on to magazine capacity.
Magazine Capacity
Proponents of 9mm pistols love to cite the fact that 9mm magazines have higher capacity than 45 ACP alternatives – and they are 100% correct.
A standard Glock 17 magazine holds 17 rounds of 9mm. A Glock 21 magazine? Only 13 rounds of 45 ACP.
The benefits of having more ammo during a life-threatening altercation go without saying. This gives the 9mm a distinct advantage. Any sensible shooter should prefer having more shots at their disposal over fewer.
Be aware of your state laws. Some states, like New York and California, restrict “high-capacity magazines”. In these cases, the 9mm’s higher capacity may not necessarily matter. A standard Glock 43 magazine holds six rounds of 9mm, whereas a Colt 1911 Defender mag holds seven!
All other things being equal, the 9mm allows you to carry more ammo. That is undeniably a distinct advantage over the 45 ACP.
| Pistol | Caliber | Standard Magazine Capacity |
|---|---|---|
| Glock 17 | 9mm | 17 rounds |
| Glock 21 | 45 ACP | 13 rounds |
| Glock 43 | 9mm | 6 rounds |
| Colt 1911 Defender | 45 ACP | 7 rounds |
Recoil
The 9mm Luger has approximately half the recoil of the 45 ACP, with 4 to 5 pounds of free recoil energy (7 to 8 pounds of free recoil energy for the 45 ACP). The 9mm cartridge fires lighter bullets at higher velocities, whereas the 45 ACP fires heavier bullets at lower velocities.
Recall your Newtonian physics: “For every action, there is an equal and opposite reaction.” That’s why the heavier powder charge and bullet of the 45 ACP generate heavier recoil than the 9mm, even if its muzzle velocity is significantly lower.
There is one caveat to this, though: firearm choice.
A classic steel-framed 1911 is considerably heavier than a polymer-framed Glock 21, M&P45, or Ruger SR45. That added weight reduces the amount of recoil that reaches the shooter’s hands.
This is the main reason why 1911 owners often say the 45 ACP doesn’t have much kick.
That being said, 9mm handguns generally do have less recoil. That allows for faster follow-up shots, as less recoil leads to less muzzle rise (i.e. the physical force that throws the sights out of alignment).
Less recoil also tends to lead to improved accuracy and shot placement. And as I’m sure you’re already aware, shot placement is key to stopping a threat.
Many shooters find that they are more accurate firing a 9mm. This is often due to its lighter recoil. The gentler-recoiling 9mm allows shooters to focus more on the fundamentals of shooting (trigger control, sight alignment, grip, stance) and develop good habits (rather than bad ones, such as recoil anticipation).
Continue reading 9mm vs. 45 ACP: The Greatest Pistol Caliber Debate on Ammo.com
https://ammo.com/comparison/9mm-vs-45#45-acp-vs-9mm-velocity-and-accuracy
