Firearms owners and Second Amendment advocates are a passionate group of people. Promoting self-reliance, freedom, and responsible gun handling, our community tirelessly advocates our position both on and off the Internet.

But if you really want to see sparks fly, ask any group of gun owners to pick their favorite between popular ammunition calibers. If you’ve spent any time on gun forums, you know that one of the biggest debates is 9mm versus .45 ACP. Both pistol cartridges are widely used for self-defense purposes. Both have fiercely loyal fanbases promoting their choice with religious fervor.

Each camp never grows tired of smearing the other. 9mm proponents call .45 ACP “.45 AARP,” implying that users of the caliber are often 55+. Likewise, .45 ACP folks love to call 9mm the “Eurotrash” caliber, since the round was originally developed in Germany.

All mudslinging aside, the core issue remains: which one is best for self-defense?

Selecting the most appropriate pistol caliber for self defense is important for any armed citizen. While each cartridge has its pros and cons, the ultimate decision of caliber selection lies with the individual user and their use case.

But the devil is in the details. From the history of both calibers to their relative merits, let’s examine the advantages and drawbacks of these popular cartridges — and possibly crown a winner.

History of the 9mm Pistol Cartridge

If you don’t know much about firearms, you might think the 9mm pistol cartridge is a fairly new invention. In reality, the cartridge is 122 years of age.

Invented in 1901 by Austrian Georg Luger, the 9x19mm Parabellum (“For War” in Latin) cartridge has long been a mainstay of European and US militaries and law enforcement. NATO even made it an official standard for pistol ammunition (STANAG 4090).

Initially, the 9mm cartridge was developed as a military round. As part of an ongoing partnership with German munitions firm Deutsche Waffen- und Munitionsfabriken (DWM), Luger debuted the cartridge to world militaries. The British turned it down, mainly since it wasn’t a British design. The US military turned it down for the same reasons — ironically, they were adopting the .45 ACP pistol cartridge instead.

The main market for 9mm for the first part of the 20th century was almost exclusively European government entities. It found rapid adoption with the German Navy in 1904, and the German Army followed suit in 1908. Weapons chambered in 9mm ended up in the hands of US forces as well, usually as battle trophies. Since the laws concerning “bring backs” weren’t yet in existence, the 9mm eventually developed a small cult following on our side of the pond.

But the initial groundwork for 9mm dominance in the US market came about in 1968, when the Illinois State Police adopted the Smith & Wesson Model 39 semi-automatic pistol as their duty sidearm. Overcoming “not invented here” syndrome (at least for the ammunition) the Model 39 proved popular especially with younger ISP officers who weren’t as tradition-bound around revolvers.

The Rise of Glock Popularity

The major surge in the popularity of the 9mm cartridge wouldn’t happen in the United States until the 1980s, when Gaston Glock imported the 9mm GLOCK 17.

With a polymer frame and a then-unusual aesthetic, the GLOCK 17 was a hard sell to US government users. But Mr. Glock himself recruited longtime friend and energetic salesman Karl Walter to take control of the pistol’s marketing. Already familiar with the unique US firearms market, Walter was given complete freedom to get the GLOCK “out there” by any means necessary — and that’s exactly what he did. Whether it was selling thousands of G17s to police departments and making almost no profit, or taking procurement specialists to Atlanta strip clubs (GLOCK USA is in Smyrna, Georgia) “on the house,” the GLOCK phenomenon soon took the US by storm. Pop culture name-checks didn’t hurt either, such as Cypress Hill’s “Hand on the GLOCK.”

Government and Military Adoption

At the same time, there was more going on behind the scenes with 9mm and the military world. Initially, the GLOCK 17 failed to become the standard service pistol for the US military in the 1980s (owing to some controversies in the procurement process). Seeking a replacement for the M1911 (in .45 ACP, no less), the military sought a 9mm pistol to conform with allied forces. GLOCK already had a lock on military contracts in the homeland of Austria, as well as Norway and other NATO nations. In a controversial move, the US military chose the Beretta M9. Based on the Beretta 92 of “Die Hard” fame, the M9 became the standard US military sidearm from 1985 until 2017, when another 9mm pistol (the SIG Sauer M17/18) replaced it.

However, GLOCK wasn’t entirely left out — the Coast Guard adopted the GLOCK 19 Gen 5 as their 9mm service pistol. Many other federal agencies have also made the jump to 9mm since the 1980s. In addition to the FBI transitioning to GLOCK 9mm pistols in the last decade, the notoriously-selective United States Secret Service traded in their .357 SIG pistols for 9mm GLOCKs as well.

With 9mm’s success in law enforcement, the US citizen market followed, purchasing 9mm pistols at an astounding rate. GLOCK 17s and GLOCK 19s proved to be the most popular, with other firearms such as the SIG Sauer P226, the Beretta 92, the Heckler & Koch VP9, the Smith & Wesson M&P 9, and various other “wonder nines” breaking sales records across the nation. Additionally, 9mm pistol-caliber carbines such as the CZ Scorpion EVO, the B&T APC 9, and the Kel-Tec SUB2000 proved popular as well.

Initially derided as a caliber for “mouse guns,” the 9mm Luger underwent several advancements in projectile design, especially Federal’s HST and Speer’s Gold Dot hollow points. These gave the caliber a boost in performance. Additionally, overpressure variants such as 9mm +P and 9mm NATO give compact 9mm pistols such as the GLOCK 43 an extra punch.

History of the .45 ACP Pistol Cartridge

Unlike the 9mm, almost no one mistakes the .45 ACP for a younger caliber. With a reputation spanning most of the wars and conflicts in modern American history, the .45 ACP is usually what comes to mind when someone mentions “venerable” and “gun” in the same sentence.

It is an old cartridge design by many standards, but in fact younger than the 9mm Luger. The .45 ACP was developed in 1904 by John Moses Browning. Considered to be “Gun Jesus” amongst firearms enthusiasts and Second Amendment advocates, Browning’s innovations in the world of guns include the .45 ACP and many other cartridges, such as the .50 Browning Machine Gun, aka the .50 BMG. Browning also developed several firearms, including the first companion pistol to the .45 ACP: the M1911. Additionally, the M1911 (especially surplus pieces) have become a favorite of the citizenry, owing to its reputation as an all-American invention.

Following the dismal performance of their .38 Long Colt pistols against determined Moro warriors in the Philippines conflict of the late 19th century, the US military requested a design for a more powerful pistol cartridge with at least a caliber of .45. Starting with an enlarged version of his .41 caliber round, Browning teamed up with Colt to bring forth the .45 Automatic Colt Pistol cartridge. It turned out to be a great answer to the military’s request.

Military specifications called for the .45 ACP to sport a 230 grain ball (full metal jacket) projectile, which rapidly became the default projectile weight for .45 ACP — and it still holds true today.

.45 ACP as a Combat Round

World War I proved to be the first trial by fire for the US military’s .45 ACP cartridge and M1911 pistol. Used by many American servicemen, the iconic combination of cartridge and pistol passed the test with flying colors. Several Commonwealth (British-associated) militaries also chose the cartridge and pistol for their inventories — more for the emergency use of allied American forces in theater than for their own use.

But the tale of .45 ACP doesn’t end there. The interwar years saw both the 1911 and .45 ACP remain the standard pistol/cartridge combo for the US military, with many US citizens picking up a 1911 chambered in .45 ACP as well. Additionally, the then-new Federal Bureau of Investigation allowed its now-legendary first classes of special agents to carry 1911s.

Even through World War II, the .45 ACP remained the chosen pistol (and submachine gun) cartridge for the US military. During this time, companies such as the sewing machine manufacturer Singer were tasked to turn out M1911 pistols. Firms with no practical experience in military ammunition were cranking out .45 ACP and other calibers to help the USs defeat the German war machine in Europe, and the Japanese in the Pacific.

In Korea, Vietnam, and various other conflicts, US servicemen trusted it to deliver. The .45 ACP simply stopped the threat, with fewer rounds expended. When veterans then pivoted towards civilian life, they brought their appreciation for “The Lord’s Caliber.” Many of them found jobs in municipal, state, and federal law enforcement, and equipped themselves with M1911 pistols as employers allowed.

In a controversial move, the M1911 and .45 ACP were retired from regular military service in 1985, in favor of the 9mm Beretta M9. But the M1911 and .45 ACP are still widely used in military service, usually by individual officers with the rank and influence to carry what they want, and special operations units where interoperability concerns are secondary to choosing the proper weapon for the mission.

The Notorious Tommy Gun

No discussion of the .45 ACP is complete without mentioning the Thompson (aka the “Tommy Gun” or the “Chicago Typewriter”). In both its semi-automatic and automatic configuration, the Tommy Gun got its start during World War I as a rapid-fire weapon (chambered in .45 ACP) used to clear enemy trenches of soldiers.

Also nicknamed the “Trench Broom,” the Tommy was also chosen by US law enforcement officers, and ordinary citizens who could afford it. Unfortunately, gangsters chose them, too.

With Prohibition in effect, organized crime increased dramatically in the US in the 1920s, leading up to the Valentine’s Day Massacre in Chicago in 1929. Four unknown assailants (some using Thompsons) murdered seven members of a rival gang. The perpetrators, suspected associates of Al Capone, escaped by posing as Chicago police officers.

Sadly, the federal government used the event as an excuse to introduce the first major federal gun control bill in history: the National Firearms Act of 1934. Among other measures, it mandated a $205 tax stamp on machine guns (like the Thompson),a large sum of money at the time This put the Thompson out of the reach for most Americans. Nonetheless, the .45 ACP cartridge continued as an American favorite.

.45 ACP Development Over the Years

Like 9mm, .45 ACP has evolved with ballistics and projectile development. Today, .45 ACP has dedicated defensive offerings such as Federal Premium’s 230 grain HST hollow point projectile, and Speer’s 230 grain Gold Dot hollow point. .45 ACP also has an overpressure variant: .45 ACP +P.

In addition, .45 ACP adherents aren’t limited to the 1911 today. GLOCK offers several pistols in .45 ACP, including the GLOCK 21, the GLOCK 30, and the GLOCK 36. FN offers the FNX-45, their submission for the canceled Joint Combat Pistol program, now available for citizen use. Heckler & Koch offers their USP in .45 ACP along with the famous Mark 23 in the same caliber.

.45 ACP’s cultural influence cannot be denied either. It’s often regarded as an “old man’s caliber,” but many young shooters have taken to it — and for good reason. Drawn by its all-American reputation and unquestioned terminal ballistics, .45 ACP fans have adopted the motto “.45 ACP — because shooting a threat twice is stupid.” Far from being consigned to the dustbin of history, .45 ACP will endure in the firearms scene for many decades to come.

Ballistic Comparison of 9mm and .45 ACP

Both 9mm and .45 ACP have proven their worth as pistol cartridges on both the street and the battlefield. Both have served citizens, law enforcement professionals, soldiers, and irregular freedom fighters around the world for over a century. It’s no wonder the debate still rages on.

As a shooter, you should be comfortable with both calibers to be most effective in an armed self defense situation. At the same time, your training, temperament, and other factors dictate that you will likely favor one cartridge over another. That’s okay, too. As an American, it’s your right to be wrong.

Choosing the right caliber for self-defense requires balancing stopping power and recoil with comfort. With your life on the line,you don’t want to rely on something you can’t effectively handle.

To help choose a caliber for your defensive needs, get to know its terminal ballistics, felt recoil, and accuracy.

By the Numbers: 9mm vs .45 ACP

No ballistics chart can replace adequate range time. However, here are the relevant statistics for 9mm and .45 ACP to give you an idea for how they perform:

Read on for an in-depth comparison of these two calibers’ performance.

9mm vs .45 ACP: Terminal Ballistics

Terminal ballistics is the behavior of a projectile when it impacts a target. Bluntly put, it’s what the bullet does when it impacts a threat.

To compare 9mm and 45 ACP, let’s assume the following factors:

• A shooter with the same skill level
• A similar-sized gun
• The same threat (a human assailant)

The .45 ACP’s larger size means it will dump more energy into a threat upon impact than the 9mm, so it will require fewer successful hits to incapacitate an attacker.

Likewise, a large .45 ACP hollow-point projectile will create a larger wound cavity in a threat, with a greater chance of central nervous system disruption and more severe blood and bodily fluid loss. The more blood flowing out of a threat at a faster rate means the threat has less time to continue their attack. Yes, it’s gruesome — but important to consider.

While some smaller 9mm projectiles dump less energy into a target and require more shots, most modern hollow points perform just fine in this area. Plus, the higher velocity of the smaller 9mm projectile means you can typically deal with threats at longer ranges, with more time and opportunities to stop an oncoming threat.

The lighter projectile weight of 9mm also means less of a drop due to gravity, allowing for more hits in vital areas at a given distance. The drop of .45 ACP is more severe, which also detracts from its usefulness at longer ranges.

How It Feels: Handling 9mm vs .45 ACP

In a gunfight, shot placement is everything.

A successful hit by a large caliber such as .45 ACP on a threat’s leg is less meaningful than a 9mm hit center mass (i.e. the torso of a threat). Even if they are bleeding out from a wound to the thigh, a threat may still be able to press a trigger. That’s why shot placement is more critical than the size of your round. If a round doesn’t allow you to place accurate shots, it’s useless to you.

With that in mind, let’s compare 9mm and .45 ACP for felt recoil, accuracy, magazine capacity, and more for an idea of how each feels in everyday use.

Felt Recoil / Accuracy

Industry professionals often speak of accuracy by analyzing felt recoil. Certainly, the size of the weapon factors into felt recoil, but the ultimate deciding factor is the choice between standard pressure or +P rounds.

While .45 ACP has arguably superior terminal ballistics, the felt recoil of .45 ACP (best described as a heavy “shove”) can be problematic for newer shooters and those with smaller frames. To achieve a meaningful level of accuracy using .45 ACP will take more training as compared to 9mm — especially with follow-up shots.

9mm is a more forgiving round, and more suitable for a wider range of shooters. This is why most law enforcement agencies and the military have switched the bulk of their forces over to 9mm.

Magazine Capacity

Of course, the milder recoil of 9mm can require more follow-up shots. The smaller projectiles, assuming a successful hit, will not cause as much nervous system disruption and blood loss in a threat. Luckily, many 9mm pistols offset this drawback by offering higher-capacity magazines. Where a GLOCK 30 in .45 ACP can only hold 10 rounds in its standard magazine (plus 1 in the chamber), a similarly-sized GLOCK 19 in 9mm can hold 15 rounds (plus 1 in the chamber) in its standard magazine.

This also makes 9mm more suitable for situations with multiple threats. A magazine change takes an eternity under duress, and in that frightening interval, a threat can regroup and attack. In some cases, having more is simply better.

Using a Suppressor

For shooting with a suppressor or silencer, .45 ACP does have an edge.

Silencers are legal to possess in 42 states (though they are still subject to taxation and paperwork requirements courtesy of the federal government). Despite the arduous process of legally acquiring a suppressor, they are popular accessories today, especially for home defense.

Unsuppressed gunshots in an enclosed space are insanely loud. You’ll almost certainly suffer permanent hearing loss after defensive gun use at home. A suppressor reduces the 150+ dB of a gunshot down to below 130 dB or more in most cases. This is still loud, but no more than a heavy metal concert.

Using a suppressor with your average 9mm rounds, only the initial “boom” of the round leaving the gun is suppressed. The round will still usually break the sound barrier, leaving a noticeable boom in its wake.

However, the .45 ACP doesn’t have this issue, as it is naturally subsonic. Though only useful across a shorter range, the subsonic characteristics make this round ideal for suppressed shooting, giving it an edge in home defense. If you’re planning on shooting suppressed, give serious consideration to .45 ACP. Your ears will thank you.

Choosing the Right Caliber Of Ammunition for a Defensive Pistol

You’ll need to consider many variables when choosing the right ammunition caliber for a defensive pistol. Here are the two primary concerns for most shooters:

Your Physical Capabilities

As a shooter, can you grip a larger pistol (i.e. a 1911 or similar .45 ACP pistol) properly? Even compact .45 ACP pistols are “fat” around the grip. Can you handle the recoil? Even the “shove” of .45 ACP can degrade accuracy significantly, so put in your range time with a .45 ACP before you bite off more than you can chew.

A 9mm is more forgiving and is more easily adopted as a defensive firearm by a wider range of shooters. Even compact 9mm pistols can accommodate up to 15 rounds of ammunition using double-stacked magazines. A smaller pistol with a significant capacity can also be more suitable for concealed carry, lending itself to less “printing.”

Remember also that shot placement is almost always more important than dumping a ton of energy into a target. Both of these rounds are sufficient to take down an assailant — it’s a question of what you need and what you can handle.

Legal Considerations

Be mindful that some states still have magazine capacity limits for non-governmental people. In these states (like California), you may be better off with a 10-round .45 ACP pistol where each round delivers more stopping power (assuming a successful hit).

Training can overcome a lot of the “deficiencies” of .45 ACP, but a threat won’t wait for you to finish your defensive courses. Ultimately, the deciding factor is if you can accurately deliver shots center mass with a given pistol cartridge and stop the threat.

Conclusion

Undoubtedly, if there were a global standard for defensive pistol ammunition, it would be 9mm. NATO standardized on the caliber decades ago, and after a brief affair with .40 S&W, US law enforcement agencies at all levels did the same. Even the United States Secret Service, who can requisition whatever they need to safeguard their principals, ditched the hot-rod .357 SIG for the 9mm in the latter part of the 2010s.

Regardless, the debate between the 9mm and .45 ACP rages on, and will likely do so for another century — or until civilians have access to laser rifles and none of this matters anymore.

Still, despite the success of 9mm, .45 ACP sales remain steady, and new converts to “The Lord’s Caliber” appear every day on forums like Reddit, and social media channels. It’s up to you to decide which one you like best.

If you’re looking for self-defense ammo for your handguns and a reliable supplier to keep your EDC gun fed and happy, you’ve come to the right place. At Pro Armory, we’ve got ammo in almost every caliber — in small boxes and bulk cases. Check out our stock of 9mm and .45 ACP ammo for your concealed carry or training pistol today.