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9mm vs. 45 ACP

9mm vs .45 ACP – What’s the Difference & Which is Better?

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One of the most prolific debates amongst all firearms loving people around the world is simply this; which handgun caliber is better, 9mm of 45 ACP? 

Today we are going to explore these two calibers and attempt to better understand the nuances and characteristics of 9mm and 45 ACP and see how they compare to one another.


The most prolific handgun caliber in the world is known by many names; 9mm, 9×19, 9mm Parabellum, 9mm NATO, etc. “9mm Luger was developed at the turn of the 20th Century; based on the .30 Luger, the case was necked up to accept the larger .355 bullet.” 

Additionally, the cartridge case and the overall geometry of this loading lend itself to more reliable feeding from a magazine. When it comes to the United States Armed Forces, “for more than 30 years, the Beretta M9 and M9A1 have been the standard sidearm of the US Army, Navy, Air Force, and Marine Corps,” only recently being replaced by the Sig Sauer P320 family of handguns, the M17 and M18, still chambered in 9mm.

9mm bullet


45 Automatic Colt Pistol, a.k.a. 45 ACP, “was also developed at the start of the 20th century by John Moses Browning. It was adopted by the U.S. Army as the standard chambering for the iconic M1911 service pistol. 

The cartridge also saw expanded use in submachine guns.” 45 ACP enabled shooters to be able to shoot a large diameter projectile, with a significant grain weight, reliably out of an automatic handgun (automatic referring to the weapon being self-loading). 

The mythical pairing of the 1911 pistol chambered in 45 ACP venerably served the United States Military for over 80 years as its primary issued sidearm, with the cartridge and or 1911 variants still being used in limited roles by specialty units to the present day.

What are the differences between 9mm and .45 ACP

Modern shooters have the luxury of being able to choose handguns that are often times chambered in multiple calibers, but still retain the same fit, feel, and sometimes parts across the different models and chamberings, with the best example of this being Glock pistols; the size and feel of the guns vary by caliber, but the overall layout, controls, manual of arms, etc. is identical. Each caliber has its own unique and interesting characteristics to consider.

9mm45 ACP
Case TypeRimless-TaperedRimless-Straight
Average Weight108 to 147 Grains68 to 300 Grains
Bullet Diameter0.355”0.451”
Velocity Range950-1400 FPS700-1150 FPS
Max Pressure34,084 PSI19,000 PSI
Overall Length1.169”1.275”
CreationGermany in 1901America in 1904
CreatorGeorg LugerJohn Moses Browning
1st Common HandgunLuger P08Colt 1911
Military UseWWI to PresentWWI to Present
Average Capacity6-20 Rounds6-14 Rounds
Average Penetration8 – 40″11.3-27”
Cost Per Round in 2022*$0.392-$27.614$0.236-$38.00
The differences between 9mm and .45 ACP

(*Cost per round in the USA is subject to drastic variations based on current market factors, however, 9mm can usually be characterized as being cheaper than 45 ACP)

9MM VS. 45 ACP


The FBI standard recommendation for penetration depth is 12-18″. This standard can easily be tested on ballistic gelatin blocks. These gel blocks mimic soft tissue and as a result, can be used to generally determine and interpret the penetration and lethality of a projectile; if a projectile stops in the first few inches it will likely not cause any major internal damage to a threat. Conversely, if a projectile rips through a gel block, it can be assumed the round will exit the threat and continue on with significant velocity.

On average, 9mm FMJ loads will penetrate between 8” to 15.9”, with some defensive loads achieving 40”. Also, depending on the ammunition choice, defensive 9mm bullets can expand from 0.35” to 0.72”. (It is important to note this data is a generalization of ballistics for this caliber and does NOT represent all loadings and capabilities of this cartridge.)

On average, 45 ACP FMJ loads will penetrate between 11.3” to 14.3”, with some defensive loads achieving 27”. Also, depending on the ammunition choice, defensive 45 ACP bullets can expand from 0.45” to 0.75”. (It is important to note this data is a generalization of ballistics for this caliber and does NOT represent all loadings and capabilities of this cartridge.)


Recoil can be defined as, the way after you fire a gun, in which the gun compresses the spring within in the handgun, causing the handguns slide to rapidly move rearward, eject the spent case, and rechamber another, with the spring pushing the slide back into the battery. This sensation is physically transmitted throughout the body, but mainly through the arms, neck, and upper torso.

Dimensionally, 9mm is smaller than 45 ACP in every way. 9mm can be loaded lighter than 45 ACP, but 45 ACP can be loaded to a heavier grain weight. Comparatively, 9mm has lighter recoil than 45 ACP, allowing for faster follow-up shots.

 This makes 9mm a more comfortable caliber to shoot, allowing for a more diverse group of shooters to wield this caliber. Also, because the cartridge is smaller in overall size, the mass and mechanics of most handguns further minimize the felt recoil of 9mm, as compared to 45 ACP. 

However, for close-range self-defense situations, recoil is not necessarily as perceivable given an individual is trying to defend themselves and the rush of adrenaline, instincts, and tunnel vision can temporarily minimize the perceived effects of recoil.

9mm vs .45


Velocity is the measured speed at which the bullet, the projectile, travels over a given distance. Since handguns and handgun calibers are used at shorter distances, velocity loss is not as big of a factor as compared to someone trying to engage a target at long distances with a rifle. 

Generally speaking, 9mm has a higher muzzle velocity than 45 ACP. This is largely due to the fact 9mm bullets are typically a lighter grain weight. However, due to the fact that 45 ACP travels slower and does not break the sound barrier, it is an easier caliber to suppress. 

9mm can also be loaded to reduce its rapport, but the inherent nature of 45 ACP being subsonic makes it a popular choice for folks to shoot suppressed.


With regards to capacity, 9mm is smaller in all its dimensions compared to 45 ACP, therefore from the factory 9mm handguns normally have more capacity. As previously mentioned, modern shooters have the luxury of choosing the caliber of a given type of handgun. 

Some shooters may choose to have less capacity but a larger bullet with 45 ACP, whereas others will want the maximum capacity in the same footprint and opt for 9mm. Modern shooters also have the luxury of opting for higher capacity magazines or magazine components to increase the amount of ammunition onboard. 

This provides shooters with a level of customization and flexibility that was not widely utilized when these calibers were first created.


With modern manufacturing and decades of small arms development, both calibers are extremely accurate. Due to the softer recoil impulse, 9mm shooters can be slightly more accurate due to the increased comfort of the cartridge. 

However, most shooters could practice and achieve similar levels of accuracy with 45 ACP. Statistically speaking, “LEOs have a 20% to 30% accuracy rate in shootouts, so magazine capacity is important,” and in employing this metric, accuracy is measured by volume of fire, not by anything inherent to either cartridge. Weapons technology has progressed to the point where, often times, the shooter is the weakest variable.


9mm is more commonly available, produced by dozens of manufacturers across the world, widely used in sport, duty, and recreational applications, and takes less material to make. Therefore, 9mm is always going to be cheaper than 45 ACP due to its economy of scale. 

45 ACP is shot and made outside of the United States, but it does not share the same proliferation that 9mm does globally. As of 2022, both calibers can be had in the U.S. for under $0.40 a round, with most defensive loads costing between $1.00 to $3.00 per round. Both calibers are fairly cost effective to train with and practice with.


9mm vs .45ACP – the pros and cons

Handguns chambered in 9mm tend to be less expensive, both ammo and the handgun, have worldwide availability, are ballistically effective at stopping a threat, and have a higher magazine capacity. Some drawbacks are the ammo has lower ballistic energy on target, a reduced lethality on larger targets (people, animals, etc.), or a less confident “feel” in the handgun given their lightweight construction.

Handguns chambered in 45 ACP tend to deliver higher muzzle energy, give shooters more stopping power, and have an overall “solid” feel-in-the-hand due to their more robust construction. However, ammo could be difficult to source depending on location, domestically or internationally, and both the guns and ammo itself are more expensive due to the smaller economy of scale associated with 45 ACP.

Which is better the 9mm or the .45?

9mm vs 45 ACP, WE END THE DEBATE by Garand Thumb

In the world of firearms, case use, personal preference, cost, and a multitude of features will dictate what constitutes as the “best” option. It is important to know that due to modern ballistics and material science, 9mm and 45 ACP, along with most handgun calibers, have very similar wound tracks. 

This has been tested and proven time and time again, with the FBI’s “Handgun Wounding Factors and Effectiveness,” report being the most commonly cited source. 

If we define “better” within a self-defense context, we see that both calibers can be effective at neutralizing a threat. Some people have a personal preference between the two calibers, with some people liking the “heavier” feel of 45 ACP handguns, while others prefer the “slim” nature of 9mm pistols. 45 ACP pistols can be quite large and may not be an ideal carry gun, but manageable as a house or vehicle weapon. 

The more compact nature of 9mm handguns lend themselves better as concealed carry weapons, but could also be pressed into service as a bedroom or truck gun.

In conclusion

Both of these calibers are widely used by not only military and law enforcement, but also by responsibly armed citizens all over the world. 9mm and 45 ACP have clearly proven to be two of the most popular calibers among handgun shooters, and they each have unique characteristics and considerations. 

9mm clearly has the larger market share and is by far more popular, both in America and internationally. 9mm is widely used by shooters in all situations and applications, whereas 45 ACP is relegated to more specialty uses. Also, due to modern developments, the old adage of big and slow for handgun lethality is no longer as relevant as it was 100 years ago.

Both calibers are regularly used by professionals, with 9mm having a majority share as of late. 9mm and 45 ACP have been proven to be very lethal cartridges time and time again, in all conflicts from WWI to the present day. 

Overall, an individual or organization has to consider all their options and select a caliber and the corresponding weapons based on what they consider to be most important. 9mm may have the larger following, but 45 ACP users are far from waving the white flag on this debate.

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