Difference Between 9mm and .45 ACP

Edited by Diffzy | Updated on: September 03, 2023


Difference Between 9mm and .45 ACP

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One of the most contentious discussions in the guns field is the argument between the 9mm and .45 ACP cartridges. Due to their widespread use and accomplishments in the field, both handguns have a sizable following. Many individuals may argue that the 45 is superior because it fires a bullet of a larger caliber or that the 9mm is superior due to its capacity. Both of the arguments are convincing and make it clear why one should be chosen over the other. Even if you believe that size > capacity or more bullets are better, you must recognize that bigger bullets and more available bullets are both important factors to take into account when deciding which pistol to use. The truth is that neither pistol has a clear edge over the other, and which handgun is best for you will depend greatly on your preferences. Let’s discuss the difference between both of them to make a clear understanding.

9mm Vs. .45 ACP

The debate between 9mm and .45 ACP has existed for more than a century. After Americans utilized their .45 caliber rifles to defeat the Germans’ 9mm, many people thought that the two World Wars provided the answer. Many .45 ACP loads indeed perform on par with the best 9mm ammunition. The best 9mm loads, however, are not equivalent to the greatest .45 ACP loads if recovered-bullet diameter and penetration imply what we believe they do. A first-grader can observe that a 9mm pistol has a higher ammo capacity, but most civilian self-defense shootings are ended with one to eight rounds. Therefore, capacity might not be that crucial. The muzzle velocity of 9mm rounds is higher than that of 45 ACP bullets. That results in deeper bullet penetration, given that the 9mm is smaller than the.45 ACP. The 9mm often has a shorter vertical drop than the 45 because of a higher muzzle velocity and lighter weight. The majority of 9mm handgun magazines hold 12 to 15 rounds, while some pistols have absurdly large capacities. The majority of .45 ACP weapons, though, are 1911s. These usually have a maximum capacity of 8 rounds per magazine, or up to 15 if one of those ridiculous-looking extended magazines is used.

Difference Between 9mm and .45 ACP in Tabular Form

Bullet Diameter9.01 mm (0.355 in).452 in (11.5 mm)
Neck Diameter9.65 mm (0.380 in).473 in (12.0 mm)
Case length19.15 mm (0.754 in).898 in (22.8 mm)
Maximum Pressure235.00 MPa (34,084 psi)21,000 psi (140 MPa)
Used byNATO and others; Militaries, police, and self-defense.United States and others
CostCheaper than .40 S&W &.45 ACPMore expensive than .40 S$W and 9mm
Case Capacity0.862 cm³ (13 gr H2O)25 gr H2O (1.625 cm³)
Primary TypeBerdan or Boxer small pistolPrimary large Pistol (but also small pistol in some brass)
Felt RecoilLess recoil.heavier and force one's hands downward rather than upward. lacks significant muzzle flip.
Variants9 mm NATO, 9×19mm Parabellum +P, 9×19mm 7N21 +P+, 9×19mm 7N31 +P+.45 ACP +P, .45 Auto Rim, .45 Super

What is 9mm?

Although specifics vary based on the type of pistol, 9mm guns normally have a higher magazine capacity than a.45 due to the smaller size of the bullet. A 9mm recoils less than a.45. This increases accuracy and makes handling the 9mm easier. The 7.65x21mm Parabellum of the Luger was converted into the 9mm cartridge. That cartridge's bottleneck was eliminated, leaving behind a tapered, rimless cartridge. In 1904 and 1906, it was adopted by the German Army and Navy, respectively. It gained more fame after World War I. Since then, it has grown to be the most widely used caliber for military and law enforcement organizations worldwide, including those in the United States. It is favored for self-defense as well.

An Australian gunsmith, George Luger created the 9×19mm Parabellum in 1901. The 7.65 x 21mm Parabellum, the predecessor to the 9mm Parabellum, was created by Luger. At the Springfield Arsenal in 1903, he competed with Browning and the 45 ACP by presenting the 9mm Parabellum to the US military for consideration. The German Army and Imperial Navy both adopted the 9mm in 1904 and 1908, respectively, before the US military did so a significant amount of time later.

Other names for the 9x19mm Parabellum include the 9x19mm NATO, 9mm Luger, and just the 9mm. The SAAMI specifications state that the maximum pressure for 9mm ammunition is 35,000 psi and that standard 115-grain FML ammunition will have an average muzzle velocity and muzzle energy of 1180 fps and 335 foot-pounds, respectively. The 9mm Luger cartridge and the Luger P-08 handgun that it was designed to go with became one of the most widely used handgun cartridges in Europe for military and law enforcement purposes after World War 1 and during World War II. But until the US Army adopted the Beretta M9 Service Pistol in the 1980s, the US was late to the party, sticking to the maxim "Bigger Bullets are Better" and our cherished 45 ACP. In the 1980s and 1990s, the emergence of incredibly dependable semi-auto handguns like the Glock 17, Sig Sauer P226, and, more recently, the Springfield XD and Smith & Wesson M&P, led to a significant increase in the popularity of the 9mm Luger in the United States.

Due to its large magazine capacity, great stopping power with jacketed hollow point ammunition (JHP), and low cost per cartridge, the 9mm has come to be associated with police enforcement and home defense. All major gun companies, including Glick, Smith and Wesson, Sig Saucer, Kimber, Springfield, Remington, Ruger, and Taurus, to mention a few, carry some 9mm handguns on their shelves, making them very accessible and reasonably priced.

9mm pistols will have less recoil and enable faster follow-up rounds since shooters can quickly refocus their sights. Additionally, less recoil usually results in more accurate and well-placed shoots. And as you are undoubtedly aware, the right shot placement is essential for neutralizing a threat. Due to decreased recoil, many shooters find that they are more accurate while using a 9mm. Shooters can concentrate on the fundamentals of shooting (trigger control, sight alignment, grip, and stance) and form positive habits instead of undesirable ones like recoil anticipation because of the 9mm's milder shooting characteristics.

What is .45 ACP?

Famous American gun designer John Moses Browning created the 45 ACP (Automatic Colt Pistol) in 1904. Many innovations, including the 45 ACP, were motivated by a need. The US Cavalry became dissatisfied with theirs.38 Long Colt side arms during the Philippine-American War due to the lack of stopping capability they offered. The Moro Rebellion was the main fight that sparked this discovery. Cavalrymen there reported that Moro warriors were absorbing shots from there.38 Long Colt revolvers without pausing. The US Military concluded that larger bullets with greater stopping power were necessary and that the 45 caliber was the best choice for this task in part because of the popularity of the 45 Long Colt. The renowned Colt Single Action Army revolver served as the Cavalry's previous standard-issue sidearm. John Moses Browning and Colt had previously been collaborating to create a new 41 caliber for consideration. However, Colt and Browning changed the caliber to 45 when this new order from the US Military arrived. The 45 ACP was substantially shorter than the 45 Schofield and 45 Long Colt, but it nonetheless replicated their ballistic characteristics. Initially, a 200-grain bullet would have been fired at 900 fps by the new 45 ACP cartridge. The finalized version, however, included a 230-grain full metal jacket (FMJ) fired at 850 fps after some adjustments by the Frankford Arsenal, Union Metallic Cartridge, and Winchester. A handgun submission was made in 1906 by Colt, using Browning’s design, along with 5 other gun makers. 1910 saw the selection of only Colt and Savage Arms. Testing conducted thereafter by the US military revealed that the Savage sidearm had 37 stoppages, whereas the Colt submittal had zero failures. As the Model 1911, the Colt handgun was chosen.

The Colt 1911 with the 45 ACP served as the standard-issue sidearm and ammunition for the next more than 70 years in all branches of the US military. It helped us survive World Wars 1 and II, the Korean Conflict, and the Vietnam War. The Beretta M9 and the 9mm Luger ammunition were not adopted by the military as their service handgun until the 1980s when they decided to upgrade it. Long after the Beretta M9 was introduced, Special Forces continued to employ the 45 ACP and Model 1911, the sidearm and cartridge with the longest service lives in US history. The SAAMI specifications state that the maximum pressure for the 45 ACP round is 19,900 psi, which is much less than the 9 mm round’s maximum pressure of 35,000 psi. It is naturally subsonic, which makes it perfect for use with submachine guns or a suppressor/silencer. 230-grain full metal jacket (FMJ) Winchester ammunition with a muzzle velocity of 835 feet per second and a muzzle energy of 356-foot pounds.

The 45 ACP is a great option for home defense because of its lesser penetration. It is, therefore, less likely that the bullet will pass through Little Johnny, who is playing COD next door, the evil guy, and your internal and external barriers. Always be aware of your backstop and what is behind your target since you are responsible for every shot you fire, even when acting in self-defense. But in a city, a lesser penetration that nevertheless penetrates deeply enough to seriously harm internal organs is optimal. And the 45 ACP provides this. When kept securely in your nightstand gun vault, the increased weight of 45 ACP weapons doesn’t make much of a difference. In addition, a heavier semi-auto handgun, such as 1911, will absorb more of that 45 ACP recoil (and serves as a useful club in case you run out of ammo).

The Main Difference Between 9mm and 45 ACP in Points

  • A 9mm round will almost double in diameter when it expands from 0.355" to about 0.6". In contrast, the 45 ACP will increase similarly, doubling in size from 0.452" to roughly 1".
  • The fact that 9mm magazines hold more rounds than their 45 ACP counterparts is frequently cited by supporters of 9mm pistols, and they are completely accurate.
  • One round would sit on top of the other in a vertical orientation in the so-called “single stack” configuration of the first 45 ACP magazine designs. The 9mm, however, is smaller; the first designs for 9mm magazines use a "double stack" design, which means that the rounds are staggered diagonally as they advance up the magazine wall.
  • The Glock 21 magazine can only store 13 rounds of 45 ACP ammunition, compared to the conventional Glock 17 magazine’s capacity of 17.
  • While the 45 ACP shoots a larger bullet at slower velocities, the 9mm cartridge does it with a smaller bullet and a higher velocity.
  • The 9mm round is the best option for long-range shooting because it discharges a lighter bullet at a higher velocity, which results in less bullet drop over distance. On the other hand, despite not being the finest choice for long-range encounters, the 45 ACP is a perfect choice for suppressed firing due to its reduced muzzle velocity.
  • There are subsonic (under 1000 fps) 9mm possibilities with 147+ grain loadings that work well with a silencer, but most shooters prefer the 45 ACP in this capacity since it is so much fun to fire suppressed.


The two most popular pistol calibers worldwide are 9mm and 45 ACP. Every significant handgun seller makes at least one semi-auto weapon specifically for the 9mm Luger and 45 ACP calibers. Regarding the shape, size, grip angle, and materials used in the manufacturing of firearms, the sky is the limit. This enables you to buy a pistol that is tailored specifically for you. One benefit of 9mm pistols is that they are frequently less expensive than comparable-sized 45 ACP options. This is because a 9mm uses fewer materials than a 45, which needs sturdier construction to withstand the additional recoil.


  • https://ammo.com/comparison/9mm-vs-45
  • https://www.shootingillustrated.com/content/9-mm-vs-45-acp-a-different-kind-of-comparison/


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"Difference Between 9mm and .45 ACP." Diffzy.com, 2024. Mon. 15 Jul. 2024. <https://www.diffzy.com/article/difference-between-9mm-and-45-acp>.

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