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9mm vs. 40 S&W vs. 45 ACP: Ultimate Pistol Cartridge Battle preview image
Nov 19 2023
8 min read

9mm vs. 40 S&W vs. 45 ACP: Ultimate Pistol Cartridge Battle


Can you compare 9mm vs. 40 S&W vs. 45 ACP? Probably not, but we’re certainly gonna try!

Ever since the sun started to shine on the earth, shooters from all over have debated the classic 9mm vs. 45, and some meet in the middle at .40. You know, just to stay neutral.

While 9mm and .45 have both seen their fair share of combat, the .40 cartridge has never been employed by the U.S. Military. Even though many law enforcement personnel around the U.S. and other countries use the .40 — the 9mm and .45 are still dominant in those fields.

Let’s go in-depth on these rounds and include some ballistics, a bit of history behind them, and why they were developed in the first place. Of course, some questions will also be answered at the end of the article.

I’m sure you own a gun or two chambered in one of these rounds.

What do you use it for?

History of the 9mm

SIG SAUER Elite Performance 9mm Luger 124 Grain

The 9mm cartridge was invented by German Georg Luger in 1901 for the British Small Arms Committee and caught some eyes at Springfield Arsenal in 1903.

The 9mm would later on be adopted by the German Navy in 1904 and caught widespread affection from the German military in 1908. The Deutsche Waffen-und Munitionsfabriken, a company that had me going back and forth on their webpage to spell their name, got their hands on the round; and gave rise to the 9mm Parabellum.

The DWM’s motto, “Si vis pacem, para bellum” is where the “parabellum” came along in 9mm Parabellum. The more you know.

But there are no differences. The 9mm, 9mm Luger, and 9mm Parabellum are all the same cartridges.

The 9mm gained a lot of nods from countries all over the world after World War II, and 9mm NATO is in use by over 70 countries in the world for their military sidearms.

History of the .40 S&W

.40 S&W

The .40 round was a joint collaboration between Smith and Wesson and Winchester in 1990. It was created to mimic the FBI’s 10mm Auto cartridge in terms of performance but could double as a cartridge that can be fitted into a 9mm sized pistol.

After the 1986 FBI Miami shootout, the Fed Bois decided to start testing with the 9×19 Parabellum and the .45 ACP to replace their revolvers with semi-automatic pistols.

They also tested with John Hall’s hand-loaded 10mm rounds, and they liked it.

The .40 caliber round became the round of choice by the FBI in 1990, with Glock chomping at the bit to get their pistols in the door. Eventually, the FBI settled with the S&W Model 4006 and the Glock 22 and 23.

History of .45 ACP

Hornady Custom .45 ACP +P 230gr XTP 20 Rounds

If God were a gunfighter himself, he probably used the .45

The .45 cartridge was built by the legend himself, John Moses Browning, in 1904 to use in his new Colt semi-automatic pistol prototype.

The U.S. Military then adopted it after complaints of stopping power came about with the .38 Long Colt rounds that were issued at that time.

After the Thompson-LaGarde testing had commenced, they determined that the .45 would replace the old .38 Long Colt.

If testing the .45 round in the stockyards doesn’t scream gangster, then I don’t know what to tell you.

As we all know, the .45 round would serve the U.S. Military with the 1911 up until 1986.  

Specification Chart

DeveloperGeorg LugerBob KlunkJohn Browning
Parent Case7.65x21mm10mm Auto
Maximum Pressure (CIP)34,084 psi19,900 psi
Maximum Pressure (SAAMI) 35,000 psi35,000 psi21,000 psi
Muzzle Velocity1,225 fps 1,160 fps950 fps
Energy 383 ft/lbs468 ft/lbs461 ft/lbs
Overall Length 1.169 in 1.135 in 1.275 in
Bullet Diameter0.355 in0.400 in0.452 in
Neck Diameter0.380 in 0.423 in0.473 in
Base Diameter0.391 in0.424 in0.476 in
Land Diameter0.347 in 0.442 in
Rim Diameter0.392 in 0.424 in0.480 in
Rim Thickness0.050 in 0.055 in0.049 in

Differences Between 9mm, .40, and .45

These rounds share almost nothing in common, so the differences will be plenty. You have to remember that none of these cartridges can be shot from the same barrel due to bullet diameter and pressure.

The only true similarity I could find is .40 propelling itself at the same pressure as the 9mm.

And the more major differences are seen when you directly compare 9mm to .45.

Which leads us to our first sub-category.


Before you ask, pressure is the energy inside of the chamber that is built up due to the burning propellants from the round being fired. The pressure pretty much determines how fast the boom boom will fly out.

If you refer to the table up there, you can see that while 9mm and .40 are similar in their pressures, the .45 cartridge falls behind by about 14,000 psi.

Why does this matter?

Well, it does help with penetration and chambering the round. Remember, it speeds up the round, helping it stay flat and travel over a longer period. This is why marksmen rifles typically have more pressure in them.

Which translates into our next category.

Muzzle Velocity

Muzzle Velocity is how the speed of the bullet leaving the barrel is measured. A higher muzzle velocity also helps with keeping the trajectory of the round in a flat motion.

Again referring to the table above, you can see that the 9mm and .40 are similar in their velocities with a difference of 65 feet per second. The .45 comes out at the bottom again with a 210 feet per second difference from the .40, and 275 feet per second slower than the 9mm.

With these two categories, you should note that the rounds are increasingly heavier from 9mm, .40, and .45. A heavier bullet will slow down quicker if the pressures are not up to snuff.


This important ballistic category is measured by how hard the bullet will impact when it hits the designated target. Do note that heavier-grain bullets tend to hit harder since it is, well, heavier.

That’s why you can see that while .45 is much slower than a 9mm, when it hits the bad guy, the .45 hits with about 78 more pounds of pressure compared to the faster 9mm.

Heavier bullets seem to connect with more energy when they land on target. Different grain weights on the bullets will give you different results.

This is all dependent on the distance from you to your target, though.

Muzzle Flip (Recoil)

Muzzle flip is the result of the round and pressure leaving the barrel, which results in a recoil-like motion from the gun.

The recoil on the 9mm is relatively low compared to the .40 and .45. As a matter of fact, when shot from the Glock 17, the 115-grain weight 9mm has around 4.6 ft/lbs of recoil energy. And feels like a small “pop” that just moves the sights off target a bit.

.40 has the weirdest recoil out of the three rounds. It is a bit harder to get on target after a shot due to the snappy recoil. Not a recoil I would like on my carry pistol. You can expect about 6.5 ft/lbs of recoil energy from a 165-grain .40 shot from a Glock 23.

The recoil on the .45 is a nice little pushback. Not super friendly, but just enough to remind you that you’re shooting a .45. Expect 4.4 ft/lbs of recoil energy when shooting a .45 from an M1911A2.

Pros & Cons of 9mm

  • Usually have higher magazine capacities
  • Perfect for concealed carry 
  • Ammo is relatively cheap and easy to find
  • Many shooters have issues with stopping power
  • Higher speeds mean bullets may travel through target
  • Not ideal against larger game

Pros & Cons of .40 S&W

  • Same PSI as 9mm with more stopping power
  • Magazine capacities are higher than .45 
  • Not too much bigger than a 9mm
  • Recoil can be a bit too much when seconds count
  • More expensive than 9mm
  • Tight tolerances of .40 pistols can lead to pressure buildup

Pros & Cons of .45

  • Higher stopping power than 9mm and .40
  • Shallow penetration, good for not hitting someone beyond your target
  • Ammo is easy to find
  • Lower magazine capacities compared to 9mm and .40
  • More recoil than 9mm, but less than .40
  • .45 Pistols are heavier than 9mm and .40 pistols


Is .45 better than 9mm for self-defense?

.45 does have more stopping power than 9mm and penetrates less, which is ideal in a situation where many people are close by. But, the magazine capacity is smaller, so taking on multiple assailants might be harder.

All in all, whatever you can shoot accurately is the best for self-defense.

Is .45 deadlier than 9mm?

Yes, .45 is deadlier than 9mm. Bigger round, bigger hole, more shock when it hits the body. The .45 is renowned in the pistol world for its stopping power and is preferred by those who don’t want to shoot more than once.

Why do the police use 9mm over .45

Police use 9mm over .45 because of cost, of course. Higher magazine capacities, easier recoil, and cheaper cost per round.


In my opinion, ballistics is one of the most fun and important parts of the firearm world. Any shooter can find what suits them best, and all you have to do is experiment and find what you like best.

After all of the research, I can say that I see a .45 in my future. I have been looking at the FNX 545 Tactical, and maybe we can get a review on that soon.

What do you think about these rounds? You know what to do. Let me know down below.

Slow and easy. Happy shooting.

Written by Brian Zerbian
Brian Zerbian photo Brian is a USMC Veteran and avid gun enthusiast from New Jersey who loves to spend his time shooting, writing, listening to classic rock, and learning new things. His goal is to help new gun owners and people who are getting into guns get all the best knowledge in the simplest ways. With no technical jargon and seasoned with fun.


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