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10mm vs. 9mm: Which Caliber is Right for You? preview image
Aug 19 2023
8 min read

10mm vs. 9mm: Which Caliber is Right for You?


What a difference a millimeter makes comparing 9mm vs 10mm. Does increasing diameter slightly really make something that much more powerful? It’s not the whole story, but in this case, yes. 10mm Auto is about twice as powerful as 9mm Parabellum.

Does this mean you should run out and buy a 10mm pistol so you can be the baddest person on the block? Not necessarily. There’s more to a gun than just one single bullet’s power.

What you buy depends on what your mission is. 10mm Auto is a powerful cartridge with strong recoil, and it might not be what you need.

Why was the cartridge developed, and how does it stack up against the popular 9mm Parabellum? Keep reading to learn everything you wanted to know about 10mm vs. 9mm!

10mm Auto



The 10mm Auto (10x25mm) cartridge was developed in the early 1980s by Jeff Cooper. His goal was to create a semi-automatic pistol that would bridge the gap in performance between .45 ACP and .357/.44 Magnum revolver calibers.

This resulted in the Bren Ten, a short-lived semi-automatic pistol based on its design on the CZ-75.

While only having an initial production run of 3 years, it became famous as Sonny Crockett’s (of Miami Vice) pistol of choice.

It was initially the only gun chambered in 10mm Auto, and the Norma company started initial ammunition production in Sweden. Production difficulties and magazine issues plagued the Bren Ten, and its parent company filed for bankruptcy after a few years.

Bren Ten Two-Tone
Bren Ten Two-Tone – 10mm Auto. Source:

Usage and Adoption

Colt saved the day a year later in 1987 when they released their Delta Elite pistol, an M1911 variant chambered in 10mm Auto. The FBI adopted the caliber as its main service cartridge in 1989 after a negative experience with the 1986 FBI Miami shootout, further increasing its popularity.

Shortly after its adoption by the FBI, however, it was determined that the recoil was too much for some agents. The large size of 10mm Auto pistols also made them difficult to handle for people with smaller hands.

The initial solution was to reduce the powder load in the cartridge, called 10mm Lite or 10mm FBI. Smith & Wesson realized they could shorten the case while retaining the same bullet diameter and performance and released their shortened 10mm Auto cartridge as the .40 S&W.

The FBI then switched to .40 S&W, leaving 10mm Auto in the lurch as a niche caliber. It still finds use in a few police departments and a Danish military unit stationed in Greenland, which uses the 10mm Auto Glock 20 for defense against polar bears.

Today, there is a small but passionate fanbase for 10mm Auto pistols.

delta colt elite
Colt Delta Elite in 10mm Auto. Source: Wikimedia Commons

9mm Parabellum

9mm Parabellum


The 9x19mm Parabellum cartridge was developed by Austrian firearm designer Georg Luger in 1901 for a new pistol he was working on. His namesake pistol, commonly known as the Luger P08, was originally called the Pistole Parabellum, which is also why the 9mm round is known as 9mm Parabellum.

Usage and Adoption

The German military adopted the Luger and 9mm Parabellum in the early 1900s, and the round went on to fight in two world wars. Many military handguns and submachine guns were chambered in 9mm during WWII, and NATO officially adopted it in 1955 as its standard handgun caliber.

Adoption in the United States took longer. A few police departments adopted the round in the 1960s. Still, the caliber’s popularity skyrocketed in the 1980s with the introduction of the polymer-frame Glocks and the US military adoption of the Beretta M9 in 1985.

Since then, its popularity has only increased, and it is now the most popular handgun caliber. This means the consumer has hundreds of guns to choose from at reasonable prices. This also means that ammunition is cheap and plentiful compared to 10mm Auto.

Specification Chart for 10mm Auto and 9mm Parabellum

Specifications9mm Parabellum10mm Auto
Bullet diameter9.01mm (0.355 in)10.17mm (0.400 in)
Neck diameter9.65mm (0.380 in)10.74mm (0.423 in)
Base diameter9.93mm (0.391 in)10.80mm (0.425 in)
Rim thickness1.27mm (0.050 in)1.40mm (0.055 in)
Case length19.15mm (0.754 in)25.20mm (0.992 in)
Overall length29.69mm (1.169 in)32.00mm (1.260 in)
Standard power364 ft-lbf with 124gr FMJ @ 1,150 ft/sec708 ft-lbf with 180gr FMJ @ 1,300 ft/sec
9mm parabellum vs. 10mm auto
L to R: 10mm Auto JHP and 9mm Parabellum JHP. Source: Wikimedia commons

Key Differences Between 10mm Auto and 9mm Parabellum

Size and power

As the above chart shows us, 10mm Auto has the advantage over 9mm Parabellum in both size and power. Only marginally bigger than 9mm, 10mm is almost twice as powerful. Although this means hefty recoil, it also means brutal stopping power. Whatever you hit with 10mm Auto will have a very bad day.

The disadvantage of the extra power is physical robustness. A pistol must be big and beefy to withstand the recoil, so 10mm pistols are generally heavier and larger than a typical 9mm pistol.

The increased cartridge diameter also means fewer rounds available for use. The EAA Tanfoglio Witness in 10mm Auto holds 14+1, whereas its 9mm counterpart is 17+1, a 3-round advantage. It’s not a huge difference, but it’s definitely a factor to consider.


For self-defense use, it’s advisable to use jacketed hollow point (JHP) bullets. This is because many standard rounds have so much power that they go right through the target, endangering people and things behind it.

JHP bullets expand when they hit the target, slowing the bullet down faster and minimizing overpenetration. The standard rule of thumb is that they expand at a factor of 1.7.

That means a 9mm hollow point expands to around 0.6 inches in diameter, and 10mm can expand to around 0.68 inches in diameter, almost 13% bigger. This results in a 28% increase in area, though a significant difference.

For human-size targets, there might still be a risk of overpenetration due to the power of 10mm. If you’re using your 10mm pistol for hunting, though, get some hot ammo and let her rip.


9mm Parabellum has been around for over 120 years and has fought in two World Wars. The majority of pistols made today are in 9mm, giving a potential buyer almost every option they can think of when it comes to a handgun.

10mm Auto, on the other hand, has only been around for 40 years and was designed from the start as a niche caliber. That doesn’t mean it doesn’t have its uses, but it greatly limits the type of firearms available to the consumer.

The high power of the cartridge makes it a poor choice for a small concealed-carry gun. At the same time, having such high power in an automatic pistol means it can be used for hunting, something 9mm is a poor choice for.

Ammunition cost and availability are alos concerns for 10mm Auto. Current prices for bulk 9mm Parabellum are around 20 cents per round, whereas 10mm auto is twice the price at 40 cents. For frequent shooters, costs can definitely add up.

10mm Auto Pros & Cons

  • High muzzle energy means better stopping power
  • Larger bullet diameter means more bullet expansion with hollow points
  • One of the few handgun calibers that is good for hunting
  • Less handguns to choose from in this caliber
  • High recoil
  • Physically larger and heavier guns than 9mm
  • Less magazine capacity than 9mm
  • Ammo is expensive and harder to come by

9mm Parabellum Pros & Cons

  • Much more popular than 10mm Auto
  • Much larger variety of handguns to choose from
  • Cheaper and much larger variety of ammo to choose from
  • Smaller bullet diameter means more magazine capacity
  • Less recoil than 10mm Auto
  • Less powerful than 10mm Auto
  • Not good for hunting


Does 10mm have more stopping power than 9mm?

In general, yes. Stopping power is normally a function of power and bullet expansion, and 10mm Auto has almost twice the energy of 9mm Parabellum. A larger diameter bullet also means greater expansion with jacketed hollow point bullets, further giving the edge to 10mm Auto.

Is 10mm better than 9mm for self-defense?

It depends. 10mm Auto has better one-stop shot potential, but lower recoil for 9mm makes follow-up shots easier and more accurate. 9mm pistols are more concealable and carry more ammo than 10mm.

However, if you are defending yourself against a polar bear, I would take a 10mm.

Is a 10mm or 40 cal more powerful?

10mm Auto is more powerful. The .40 S&W is just a short-case variant of 10mm Auto.


10mm Auto is definitely an interesting round and has developed a niche in pistol hunting circles and for large animal defense, like fighting off bears.

Still, 9mm ammunition has come a long way over the years, and high power loads are still adequate for most defense situations.

9mm Parabellum has become ubiquitous, with pistol offerings from full-size, high capacity down to compact pocket pistols. 10mm Auto doesn’t offer that kind of versatility. Ammunition price and availability also heavily favor 9mm.

If you plan on going hiking and think you’ll run into Mike Ditka and the Chicago Bears, get yourself a 10mm. If you just want a versatile plinker or something concealable for daily carry, stick with 9mm. Your wallet, and your wrists, will thank you.

Written by Joel Nordness
Joel Nordness photo Joel grew up in the cornfields of Illinois. After college, he had a brief stint in California, befriending veterans at the Navy base he worked at who introduced him to shooting. Realizing how much fun shooting could be, he carried that passion with him to his new home in Indiana, where he developed a love for rare and unusual handguns and firearm history. He tries his best to keep his gun collection to reasonable levels while doing what he can to introduce new shooters to the joy of the hobby.


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