9mm cartridges

What is the Caliber of the 9 mM?-A Real Dependable Guide

What Caliber is the 9mm? 

The short answer is that the caliber of a 9mm, 9mm luger, or 9mm parabellum is 9mm….yes that is right. The one of the more popular calibers that is used by police forces around the world is 9mm aka the designation of the caliber.

Also remember the 9mm luger or any variations of the caliber is NOT a 38 special. The 9mm luger bullet is a slightly smaller bullet than the 38 special.

However, it has shocked us here at Outdoor Methods that many gun owners are excellent marksman, but still do not know what caliber really means or how it is designated. And even if you do not care let’s take a systemic approach and explain what is the caliber of the 9mm.

How is a Caliber Determined? 

The definition of Caliber, in simple terms, is a designation assigned to a specific group of guns and ammo. So for example the 9mm luger is a 9mm caliber.

Caliber designation are typically determined in one of two methods.

  1. First method designates a caliber using the dimension of a barrel’s internal diameter. An example of a caliber assigned using is this method is the British .303.
  2. Second method identifies a caliber by the actual bullet diameter . Not the cartridge but the bullet. An excellent example of this method is the 9mm luger, which was designated measuring the bullet width that is .355 inches or 9.017 mm.
9mm Rounds

So we know a 9mm luger is a 9mm caliber, and we understand how calibers are determined Great! That was easy. But wait! There is more! What is with this whole 9mm, 9mm luger, and 9×19 Parabellum? Are they the same?

Short awnser..Yes they are.

But you want a detail awnser don’t you? Great! First you need to know where this toally awesome caliber came from.

Who Invented This Awesome Yet Confusing Caliber? 9mm Parabellum vs 9mm Luger

Yes, the 9mm parabellum and 9mm luger are the same. The 9mm was originally developed by some Austrian dude in 1901 who had already deveolped a pretty amazing pistol at the time, but wanted a even more BAD A** round to go with it. His last name was Luger, and he pretty much was a Chuck Norris of the gun world.

So in 1902 the German arms manufacturer Deutsche Waffen- und Munitionsfabriken (DWM) with Luger made a semi-automatic pistol to shoot Luger’s newly invented bullet 9mm caliber round.

The Sporting Arms and Ammunition Manufacturers’ Institute (SAAMI) decided to give Luger some props and named the 9mm cartridge as the 9mm luger.

Then a new standards group developed in 1914 called Commission Internationale Permanente pour l’Épreuve des Armes à Feu Portatives (CIP) said you all are crazy. We are here, and will tell you the correct name of this caliber, and nobody can object because our official language is French…Therefore we will call this caliber the 9_mm luger. You must put a space between the 9 and the mm.

Meanwhile DWM did not feel they needed to give Luger any naming credit and officially called the 9mm the 9x19mm Parabellum. Yes, if you are still reading things are starting to get a little unnecessarily confusing

However, DWM named the caliber 9x19mm parabellum because an earlier cartridge was named 7.65x21mm parabellum. This earlier cartridge was the one use in Luger’s earlier semi-auto pistol. We know mind blown…

The word parbellum was tagged on to the end of the caliber name becuase it represents DWM’s motto, Si vis pacem, para bellum. This is Latin for “if you seek peace, prepare for war” and since they thought this was a legendary motto, which it is is, they tagged it on to the new caliber.

They also tagged it on to the new caliber becuase the offical name of the semi-automatic pistol from DWM for the 9mm was Pistole Parabellum, but the pistols unoffical name was the Luger Pistol.

The 9×19 parabellum would go on to be used armed forces in dozens of major conflicts around the world including World War I and World War II.

…But wait there is more…..

Different Variations of the 9mm Parabellum

The 9mm Luger, or 9x19mm Parabellum, is a highly effective popular caliber However, there are several variations of the standard 9mm cartridge out there, each with its own purpose and features.


The 9mm+P is an enhanced version with the same diameter of bullet as the 9mm Luger, that is typically used in a self defense situation with a slightly higher pressure and muzzle velocity.

According to SAAMI guidelines, the maximum pressure limit for standard 9mm ammunition is 35,000 psi; however, higher-powered +P ammo has a remarkable 10% increase in chamber pressure up to 38,500 psi.

As a result, you get better penetration with the +P bullet Before you use one of these make sure your gun can handle the +p pressure.

In any self defense situation you can not go wrong with a gun using these rounds

9mm NATO

The 9mm NATO are military cartridges that has the same diameter bullet as the 9mm Luger, but with a slightly higher firearms chambered pressure (at 36,500 psi) than commercial rounds.

It was designed to be used as a military caliber but can also be used in civilian-owned guns. Again, the 9mm NATO bullet has more muzzle velocity when fired and better penetration, but the standard 9x19mm has lower recoil

9mm Browning Commonly Referred as 380 ACP

The 9 mm Browning, invented by John Browning, is also known as the 380 ACP, are slightly smaller pistol cartridges than the standard 9mm, but you will never guess it has the same bullet diameter as your standard 9mm.

The 380 ACP or, 9mm short, is designed for close-range self-defense situations. We are pretty sure 007 gun shots the 9mm Browning bullet.

The 9mm Browning, also known as the 380 ACP (automatic colt pistol), is one of the oldest pistol cartridges in production. It was first designed by John Moses Browning in 1908 for his Colt Model 1903 Pocket Hammerless. The cartridge was designed with a smaller profile than most 9mm cartridges and is rimless cartridge.

9mm Ultra

Initially designed for the Luftwaffe in 1936, this technology was sadly not adopted until much later.

The 9x18mm Ultra is a German pistol cartridge that was originally developed in 1936 for use by the Luftwaffe, but was not adopted at that time. It is a rimless cartridge with a close to the same bullet diameter as the standard 9mm . It has similar chamber pressure and and muzzle velocity of the .380 ACP

Sig Sauer even got into the game of producing a gun called the P230 using these cartridges, but it did not last long.

9mm Markarow

The 9x18mm Makarov, or 9mm Makarov, is a Russian military pistol cartridge that was developed in 1946 by Boris Semin The round is rimless and is based on the 9mm Ultra design, and has a slightly larger bullet diameter than the standard 9mm parabellum.

This was a popular caliber in the Soviet Union, and even could be used in submachine guns

Inside a 9mm bullet


9x21mm vs 9mm

The 9x21mm cartridge is a relatively new round in the handgun world. First developed in Italy in 1980, it has since become a popular alternative to the 9x19mm Parabellum for tactical use in Italy and Israel. Unfortunately, some countries deny civilians the option to purchase this round.

It is a rimless, bottlenecked round that is slightly longer cast than the standard 9mm. The bullet is slightly wider than the standard 9mm as well.

At first, many did not like it due to the barrel length of their gun needing to be adjusted. However, that quickly changed and these rounds are still being fired by militaries around the world.

What Makes People like the 9mm?

  • You get a more power compared to other smaller rounds like the 38 special. As a result, you get less recoil when shooting
  • Smaller guns can be made due to the relatively small size of the cartridge which is better for concealment 
  • The 9 mm is one of the most abundant rounds in the world, making it reasonably low cost make, and therefore reasonably cheap to buy. 
  • Due to an improvement in bullet design, some 9 mm cartridges outperform the 40 s.w. and 45 acp rounds. 
  • It is the default NATO round.

The 9mm caliber has really started to become popular over the past few years because the FBI has switched to it being their default caliber for several reasons.

Glock 19 Gen4
Glock 19 Gen 4. Check out the best night sights for Glocks!

Some of these reasons are 9mm firearms have a cheaper operational cost compared to larger calibers, and studies show that FBI agents are more accurate with it compared to larger calibers.

For Concealed Carry 

Many old school gun enthusiasts will tell you that the 9mm does not have enough knockdown power. These same people will straight up laugh at you for packing a small pistol like the 38 special. However, as the FBI puts it, knockdown power is a myth, and there is no data to back up the term knockdown power.

The 9mm magazine can generally hold more rounds than most 40 s. w. and 45 acp in a smaller frame gun. This will allow you to be able to conceal your weapon easier without giving up the number of shots that you can carry while not giving up concealment. You can also find some amazing night sights for a 9 such as Glocks.

Lastly, since many people will only practice with their concealed carry weapons a few times (if at all), a gun with a smaller recoil will be more manageable for them to handle and, in theory, will mean they will be more accurate.

While we do not want you to use this as an excuse not to practice if life gets in the way where you cannot find time to shoot more than a few times a year, less recoil will be very helpful in allowing you to defend yourself if the time ever comes. 

Wrapping It Up

What is the caliber of the 9 mm? Well hate to break it to you, but it is 9 mm, and while the old school train of thought was that the 9 mm is an underpowered caliber that is not for self defense, data from the last few decades shows this is a pretty Bad A self defense weapon.

9 mm cartridges have been so heavily re-engineered that they hit above their weight class by outperforming some larger calibers. So much so that law enforcement agencies across the country and even some in the armed forces are now using it.

As for 9mm pistols, they can be designed to be smaller than most guns while still having higher magazine capacity. So next time you hear somebody talking down about the 9 mm, you can now educate them on why this is not a caliber to be laughed at. 

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