The difference between 9mm and 9mm Luger is either nothing or the latter is part of the former. Depending on how you define it.
Most of the time, when a person says “9mm,” they mean is 9x19mm, which is the most common handgun round. This is what you feed your GLOCK 19, S&W M&P or — if you actually have taste in handguns — your 9mm 1911, Browning Hi Power or CZ-75.
However, there is an entire family of handgun cartridges that uses the same size (9mm) projectile.
Why do people get them confused? Mostly it’s because of colloquial usage, as we here in the USA like our brevity, but also because we don’t like that there metric system and it’s witchery.
But I digress. To get it out of the way, the 9x19mm round itself is the 9mm Luger round. It’s also 9mm Parabellum AND 9mm NATO. It’s all the same bullet and cartridge.
The round itself was developed by Georg Luger during the design process of his famous pistol, often referred to simply as a “Luger.” The comment section will probably hate me for skipping some details, but I will just have to find a way to live with myself.
Initially, the pistol was chambered for a 7.65x21mm bullet, which Luger developed from the 7.65x25mm Borchardt cartridge…which also was the basis for the 7.63mm Mauser and 7.63mm Tokarev rounds. However, the German military felt that a larger round was probably a good idea, so he trimmed the case and inserted a 9mm (0.355-in) projectile.
Since the name of the Luger pistol was the Pistole Parabellum (basically meaning “Pistol For War”) he therefore dubbed the two rounds 7.65mm Parabellum and 9mm Parabellum, respectively. However, the authorities of SAAMI and CIP being what they are, decided to call them .30 Luger and 9mm Luger (respectively) instead.
Further compounding the confusion, NATO decided to make it their standard pistol round. NATO has their own handloading manual and created a standard load for it. The standard 9mm NATO round is a 124-grain FMJ, loaded to 36,500 psi, which is a bit hotter than the CIP standard of about 34,000 psi. (SAAMI standards are 35,000 psi.) Thus, 9mm NATO is an overpressure variant.
A 124-grain 9mm NATO round zips along at about 1200 fps and just shy of 400 ft-lbs of energy. The standard pressure 124-gr loading of 9mm is usually slower by about 100 fps (depending) and carries about 50 fewer ft-lbs of energy out of the muzzle.
So, that’s the difference. 9mm Parabellum, 9x19mm Parabellum and 9mm Luger are all the same cartridge; 9mm NATO is just a specific loading of it that’s approved by NATO for NATO use.
But I keep hearing about 9mm Browning and 9mm Makarov. What are those, you ask?
Let the hair-splitting begin!
Okay, so the 9mm Parabellum is just part of a family of handgun rounds that chamber the same 0.355-in (that’s 9 millimeters) projectile. There are a number of them, though only a few are popular in the United States.
It’s kind of like when people talk about 7mm rifles. Usually, when someone talks about “7mm” they typically mean 7mm Remington Magnum, 7mm-08 Remington or possibly 7x57mm Mauser as those are the most popular rounds with a 7mm-diameter projectile.
However, there are plenty of rounds that use the same size bullet, such as 7mm Remington Ultra, 7mm Weatherby Magnum, 7mm Shooting Times Westerner, Warren Page’s favorite wildcat the 7mm Mashburn Super Magnum, .280 Remington, .284 Winchester and .280 Ackley Improved…and more.
The most popular member of the 9mm family outside of 9mm Luger is .380 ACP, also called .380 Auto. Invented by John Browning, it uses the same size bullet as 9mm Parabellum, but in a much shorter case. The Europeans don’t know what a Big Mac or a .380 is, so they refer to it by its metric diameter of 9 millimeters. As a result, it’s called 9mm Short, 9mm Kurz (German for “short”), 9mm Browning and 9x17mm, though not 9mm with cheese.
A similar round developed in Spain around the same time as the 9mm Parabellum was the 9mm Largo. 9mm Largo, or 9x23mm, employs a longer case than the 9mm Parabellum (23mm vs 19mm) and an ever-so-slightly lesser powder charge. Basically, knock 50 fps off a 9mm Luger and you got it.
While not common in the US at all, 9mm Largo (Spanish for “long,” should you ask) is popular in some Latin American countries.
Another variant, which found some adoption among European police agencies, was the 9x18mm Ultra. The 9x18mm Ultra uses a slightly longer case than the .380 ACP — 18mm vs 17mm — and nets about 20 fps and 60+ ft-lbs more. You won’t find it anywhere, though you might find the odd SIG P230 or P232 chambered for it.
The 9mm Makarov, or 9x18mm Makarov, however, is different. 9mm Makarov employs a .365-in diameter projectile, so it’s technically 9.27mm Makarov. However, the most important thing you should know about that minor detail is that nobody really cares.
Another variant is 9x21mm, also called 9mm IMI. This round was developed by Israel Military Industries for use in countries where civilians are forbidden to purchase firearms chambered in “military calibers.” 9x21mm IMI is basically the same as 9mm Parabellum. IMI being some clever folks, they seat the bullet deeper in the case so it’s the same overall length as 9mm Para.
The competitive shooting world has also given us 9x25mm Dillon and 9x23mm Winchester. The former round is a 10mm case necked down for a 9mm projectile (sort of like .357 SIG) and the latter is (in the broad strokes) a rimless .38 Super. These cartridges meet the Major power factor of IPSC and other competitive shooting events but haven’t caught on outside of that.
Dr. Brad Miller of Shooting Times and Handguns Magazine even proposed a new variant he called 9mm Auto. The 9mm Auto is a duplicate of the 9mm Parabellum ballistically, but revises the case to straight walls. The 9mm Luger round has a slight taper (it narrows by about 0.01 inches from the base to the case mouth) which causes an exaggerated nosedive gap (the space between cartridges in a magazine) and thus causes the round to hit the feedramp at a rather low angle, which has been known to cause feeding problems in single-stack magazines. The 9mm Auto aims to correct this problem.
So…to sum up: 9mm is actually a family of cartridges, but we most often use it as short-hand to refer to the 9mm Luger, which is the most popular member of that family. Got it?