Of all the firearms debates, perhaps none is more heated today than 9mm vs .45 ACP. Originating in the early 20th century, 9mm and .45 ACP have dominated the semi-automatic pistol market for decades and remain two of the most popular rounds in the world.

A rare unserialized WW2 Singer Manufacturing Co. prototype/presentation Model 1911A1 pistol.

The .45 ACP vs 9mm showdown defined the development of 20th century pistols and submachine guns. Some of the finest vintage and modern firearms chambered for each of these iconic cartridges are available at Rock Island Auction Company. Click on the images throughout this article to learn more about each model.

An outstanding Mauser "K" Date "S/42" Code P.08 Luger pistol rig with two matching magazines and a "1934" dated holster.

9MM vs .45 ACP

Proponents of .45 ACP will point to the cartridge’s status as a two-time World War champ and its superior stopping power. 9mm advocates laud their chosen round's greater magazine capacity, ease of carry, and lighter recoil.

In the 9mm vs .45 ACP debate, capacity is often considered the most important factor. 9mm wins here hands down. The classic .45 ACP 1911 design and its single-stack magazine holds only six rounds, with a seventh in the chamber. The 9mm Browning Hi Power and its double stack magazine offers 13 rounds, while the Glock 17 has a 17 round capacity. Later .45 ACP double stack pistols still fall short in this category, with examples like the Glock 21 only able to hold 13 rounds.

An incredibly early production two-digit serial number 15 U.S. Colt Model 1911 pistol with an Anniston Army Depot shipping box.

.45 ACP is a fatter, heavier round that carves out a larger wound channel and delivers greater muzzle energy to a target without excessive penetration. Though advancements in modern hollow point bullets have helped the higher velocity 9mm bullets close this gap, .45 ACP holds the advantage when it comes to imparting more mass on impact.

That power comes with greater recoil, however. The weight and style of a .45 ACP firearm can reduce this drawback, like the classic 1911 pistols and their sturdy frames, but the lighter 9mm still holds the edge in this category.

Another advantage 9mm offers over .45 ACP is a significantly cheaper ammunition cost. Both rounds are widely available though, and every major handgun manufacturer offers pistols chambered in each of these classic cartridges.

A desirable pre-WW2 "S" code Krieghoff Luger pistol rig with two matching magazines, a Krieghoff proofed holster, and a service belt.

9mm Development

In 1901, Georg Luger adapted the 7.65 mm Luger cartridge, which had been previously derived from the 7.65 Borchardt, and created the 9×19mm Parabellum, or 9mm Luger. Modifications included shortening the case, removing the bottleneck shape, and increasing the diameter and weight of the bullet.

An excellent DWM Model 1900 Commercial Luger pistol chambered in 7.65.

The resulting 9mm round, a tapered rimless cartridge with more power than its predecessors, was created at the request of the German Military. In 1904, the German Navy adopted the Luger pistol and the 9mm round, and the Army did four years later.

The 9mm Luger would be officially adopted by Bolivia, Bulgaria, Portugal, and the Netherlands over the next few years, with the pistol becoming a standard of numerous other military branches and law enforcement agencies around the globe in the decades to follow.

A pre-WW2 9mm German Luftwaffe contract "1936" dated 9mm Krieghoff Luger pistol with matching magazine.

The 9mm cartridge saw several notable variants in its early years, including the 9x25mm Mauser, the 9mm Steyr, and rarities like the 9×23mm Largo developed for the Bergmann Mars pistol. American inventor John Moses Browning developed the 9mm Browning Long for the FN Model 1903 pistol, which was employed by France, Belgium, and several other European nations.

A scarce Bergmann Mars Model 1903 pistol in 9mm Largo.

.45 ACP Development

During the Philippine Insurrection at the turn of the 20th century, U.S. troops reported that the .38 caliber revolver lacked sufficient power to stop determined combatants. John Moses Browning had been working with Colt to develop a .41 caliber pistol cartridge. After the Thompson-LaGarde field tests concluded that a .45 caliber bullet would be most desirable, Browning scaled up both his handgun and his cartridge design in preparation for the next round of military testing, officially marking the start of the .45 ACP vs 9mm faceoff.

Winchester, Union Metallic Cartridge Co., and Frankford Arsenal would help develop the .45 ACP. Years of testing resulted in a 230 grain, full metal jacket round with a muzzle velocity of 850 fps. In short, a large slow cartridge compared to its 9mm competitor.

U.S. Army Test Trials serial number 70 Colt Model 1907 military pistol in .45 ACP.

In January 1906 Chief of Ordnance B.G. Crozier invited gun manufacturers to develop and submit a semi-automatic handguns that chambered Browning's new .45 ACP cartridge for submission into a new round of field trials. Eighteen companies initially responded with only eight actually submitting a test sample pistol, including Savage and Luger. The Savage Arms Corporation entered a version of its Model 1907 automatic pistol scaled up for .45 ACP like the exceptionally rare example below.

A rare U.S. Army Model 1907 Savage Arms .45 ACP test pistol serial number 222.

The DWM factory is believed to have originally produced one prototype and two full-size Lugers in .45 ACP for the 1907 U.S. test trials. DWM eventually withdrew its bid over concerns that the American military would not select a European manufacturer regardless of firearm quality.

The example below is the first of only a handful of custom recreations of the original DWM Model 1906 Luger test pistols chambered in .45 ACP. Produced by Mike Krause out of San Mateo, California in the late 1990s, these rare pistols exhibit the distinctive flat bottom trigger guard shape.

Serial number "01" Krausewerk custom-made Model 1906 U.S. Trials .45 ACP Luger pistol with an extra magazine.

.45 ACP vs 9mm Early Firearms

Colt would ultimately win the competition and receive a contract to produce the American military's .45 ACP semi-automatic pistol. The M1911 pistol was adopted by the Army in March 1911, with the Navy and Marine Corps following suit in 1913. The Colt Government Model, the civilian version of the M1911, found a role in home defense, law enforcement, and as privately purchased military sidearms.

When America entered the Great War in 1917, the military had less than 75,000 M1911s on hand. By the end of the conflict, Colt would go on to produce 412,114 more pistols. The M1917 revolver chambered in .45 ACP would help fill the shortfall.

A documented historic WW1 era U.S. Marine Corps shipped Colt Model 1911 pistol with a war-era "Hate Belt," photographs, and documents attributed to Corporal Andrew Liebler.

The large-frame M1917 revolver, based on Colt's New Service model, employed half-moon clips to extract and eject the .45 ACP rimless cases. With nearly 300,000 M1917 revolvers produced between Colt and Smith & Wesson, the model became a common surplus item after the war. Peters Cartridge Company of Ohio would introduce the .45 ACP Auto Rim in 1920, a .45 ACP round with a thick rim that allowed the revolver to be loaded and unloaded by hand.

A Smith & Wesson Commercial Model 1917 DA revolver in .45 ACP.

Across the pond, the 9mm cartridge had become a rising star. Though WW1 saw its fair share of European pistol models fielded, including the M1912 in 9mm Steyr and the Beretta Model 1915 in 9mm Glisenti, the Luger in 9×19mm Parabellum was far and away the most prevalent sidearm issued to German forces. According to historian Stephen Bull, about 1.6 million Luger pistols had been produced by the end of the Great War, most chambered in 9mm.

A 9mm Imperial German DWM Model 1906 First Issue Navy Luger with a Kiel Shipyard marking, a commercial export marking, and a matching shoulder stock and holster rig.

WW1 saw a revolution in arms innovation, including the first submachine gun fielded by a major military. Though Hugo Schmeisser's 9mm Maschinenpistole 18 was introduced too late to make a dramatic impact, the straight blowback weapon demonstrated the potential of an automatic firearm chambered for handgun rounds. Hugo Schmeisser's double-stack, single-feed, 9mm magazine patents would be employed in the Mp18's spiritual successors.

A Steyr MP34 submachine gun in 9mm Luger.

In America, retired army Colonel John Taliaferro Thompson had been developing a submachine gun of his own. More than a decade earlier, Thompson had served a key role in recommending the adoption of the .45 ACP cartridge, and he selected the round for his submachine gun design when .30-06 proved incompatible. The war ended before Thompson's "trench broom" could hit the battlefield, but the weapon would find a wide range of roles in the interwar period and beyond.

A Colt Thompson Model 1921 submachine gun in .45 ACP. This example was shipped in "1921AC" configuration to the Police Department of Mattoon, Illinois, on March 22, 1930.

The .45 ACP vs 9mm Faceoff Heats Up

The 1911 saw numerous clones, copies, and licensed models before and after the interwar period. The .45 ACP round became a favorite in China, with government factions and warlord militias purchasing Tommy guns and manufacturing their own copies. In the late 1920s, the Shansei Arsenal developed a Broomhandle variant chambered in .45 ACP.

In 1926, Colt introduced an updated version of the M1911. Designated the M1911A1, improvements included a shortened trigger, extended hammer spurs, simplified checkered grips, an arched mainspring housing, a thicker front sight, and angled clearance cutouts. These refinements were also present in Colt's 1932 civilian competition pistol, the National Match model.

With the winds of war stirring in Europe, the U.S. Government reached out to established arms makers like Colt, Ithaca, and Remington Rand to mass produce the M1911A1 pistol. Civilian contracts were also granted to companies like Singer and Union Switch & Signal.

Rare early production, I-prefix WW U.S. Ithaca Model 1911A1 pistol.

During the Great War, the 9mm Luger had proved itself as an effective pistol and submachine gun round, and the German war machine would continue to favor the cartridge as they developed the next generation of firearms. While the Luger remained a common secondary sidearm, the Walther P.38 became the Wehrmacht's standard pistol during WW2. The pistol saw a production run of nearly 1.2 million by the war's end.

An early First Model Zero Series Walther P.38 pistol.

Before WW2 started, another 9mm pistol hit the market in Europe and became one of the most influential designs in the genre. The Browning Hi Power was designed in the 1920s in response to a potential French military contract. Incorporating elements from his .45 ACP 1911 pistol, inventor John Moses Browning envisioned a high capacity, double-stack 9mm magazine and a magazine disconnect.

Browning passed away before the pistol was finished, but the design was completed by Dieudonné Joseph Saive of Fabrique Nationale. With a 13 round capacity, the Hi Power saw prominent use by police and military branches across Europe, including the German Waffen SS and the Fallschirmjäger. The pistol was also produced for Canadian, British, and Chinese forces.

A cased, engraved, and gold inlaid Browning Gold Classic Hi Power pistol.

.45 ACP vs 9mm Submachine Guns

America continued to rely on the .45 ACP for its submachine guns throughout WW2. Every iteration of the Thompson M1928 saw service with the Allied forces, with many M1928s being purchased by the British military. To meet surging demand, a streamlined, lower cost version of the platform was developed in 1942 called the M1 Thompson.

America adopted the M3 "grease gun" in 1943, a no-frills .45 ACP submachine gun. The M3's sheet steel design was cheaper and far more manufacturer-friendly, with 620,000 produced by war's end.

A documented law enforcement shipped Colt Model 1921/1928 U.S. Navy Overstamp Thompson submachine gun.

The British considered using the .455 Webley Automatic Mk I cartridge for their submachine guns, but they found the 9mm offered a greater range and a notably higher muzzle velocity. The lighter 9mm also allowed each soldier to carry more rounds. The 9mm Lanchester was used by the British early in the war, a model that took heavy inspiration from the German M28, but the more affordable STEN would ultimately be adopted. With 4 million produced, the STEN became the most fielded 9mm SMG of the conflict.

While the Italians produced the 9mm Beretta Model 38, the MP40 and its predecessors were the most commonly encountered SMG faced by the Allies in Europe and North Africa. Germany's straight blow-back, open-bolt MP40 employed a 32-round 9mm box magazine, providing compact firepower to the paratroopers, armored crewmen, and support infantry who carried it.

A 9mm MP40 submachine gun.

The .45 ACP vs 9mm arms race would continue with the next generation of SMG designs, but the 9mm cartridge quickly emerged as the clear favorite. Models like the WW2 Reising Model 50 that were specifically designed around the .45 ACP would become increasingly scarce, though multi-caliber platforms like the UZI, MAC-10, and Heckler & Koch UMP included .45 ACP variants.

A .45 ACP Reising Model 50 SMG. The Reising Model 50 saw action with the U.S. Marines in the Pacific as a substitute for the M1 Thompson.

In contrast, the number of 9mm submachine gun models is staggering. The British Sterling, the Smith & Wesson 76, and the Beretta M12 are just a few notable examples of the 9mm round serving as a proven SMG standard for decades. Today, Heckler & Koch's MP5 family continues to lead the market, with over 40 nations having adopted the platform and countless law enforcement and security agencies relying on this tried-and-true 9mm design.

A Hard Times Armory/Heckler & Koch Model 94 automatic rifle.

.45 ACP vs 9mm Post War

After WW2, every NATO nation would adopt the 9mm pistol cartridge except for the United States, which continued to issue the M1911A1 until 1985. In America, the revolver continued to dominate the law enforcement market, but the wheelgun would eventually be challenged by the "Wonder Nine" pistols of the 1970s and 80s.

Successors to the Browning Hi Power, the Wonder Nine moniker is a reference to a wave of 9mm DA/SA action pistols with double stack mags and lighter polymer frames. Popular examples include the S&W 59, the CZ-75, the Glock, and the Beretta 92. The latter would be adopted by the American military as the M9, finally replacing the venerable .45 ACP 1911.

A documented U.S. Beretta M9 General Officer's Pistol with holster, magazine pouch and two extra magazines.

The .45 ACP continued to maintain a steady following, and a surplus of ammunition became available in the decades after the war. Surplus guns chambered in the round hit the market as well, including M1917s and Webley revolver conversions. Smith & Wesson also offered the Model 22, Model 25, and Model 26 revolvers as the commercial successors to the M1917. The .45 ACP Model 625 continues to enjoy popularity today thanks to its use by speed shooting champion Jerry Miculek.

The 1911 was another readily available surplus handgun after the war, and the National Match returned to Colt's catalog in 1957 as the Gold Cup National Match. In 1970, the popular Colt Series 70 hit the market, and the Series 80 followed 13 years later. Today, the 1911 pistol is produced by numerous manufacturers.

A documented Colt Mark IV Series 80 Government Model pistol previously owned by Captain Jack Dean of the Texas Rangers.

In the .45 ACP vs 9mm arms race, each round has benefited from advancements in propellant and material design, but the 9mm capacity advantage that had won the cartridge such a widespread following in Europe would help the round conquer the American market as well. For law enforcement and military branches, pistols like the Glock 17 and SIG Sauer P320 offered high capacity, reliability, and ease of operation at an affordable price point.

A documented, Fort Hood shipped, U.S. Army issued SIG Sauer M17 with FOIA letter and box, serial number "TF000760"

With up to 2 billion rounds sold each year in America alone, the dominance of the 9mm round is undeniable today. The Glock, the best selling handgun platform in history, includes popular 9mm options like the Model 17, 19, 19X, 26, 34, 43, 45 and 48.

The classic 1911 still continued to be carried by select American military units and officers through the War on Terror, and today the platform and its .45 ACP cartridge enjoys popularity with shooters and competitors. Like its 9mm rival, .45 ACP pistols are manufactured by nearly every major manufacturer.

A scarce Springfield Armory Inc. Custom Shop "FBI" prefix Bureau Model pistol, serial number "FBI 25", with a Certificate of Authenticity.

.45 ACP vs 9mm Today

From pistols and revolvers to rifles and SMGs, the 120-year faceoff between 9mm and .45 ACP has resulted in some truly legendary firearms. Though the 9mm has become the clear favorite today, each iconic cartridge has stood the test of time. For the arms enthusiasts, there's always room in your collection for a vintage Luger, 1911, or a modern classic like the M17, and Rock Island Auction Company offers the finest examples chambered in each of these iconic calibers.

A rare North American Arms Co. M1911 pistol, serial number "62".

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