In most movies and video games I have observed people mentioning ammo type and capacity such as, 5.56, 7.76, 9mm, 0.50 calibrate, .45 ACP.
What are these ammo type ?
Edit1: 0.50 Calibre, my mistake!
In: Engineering
These are metric sizes:
5.56 – The bullet is 5.56mm in diameter. This is short for the full name, 5.56×45, the 45 meaning the case of the bullet is 45mm long. This is similar to the civilian .223 Remington, very slight differences but not in outer dimension.
7.76 – You probably mean 7.62×51, same meaning as above.
Neither of the above necessarily mean “assault rifle.” They were popularized by military rifles, but they are also commonly used with civilian rifles in the US. The 5.56/223 remains an excellent varmint cartridge due to its heritage (below), and it is the favorite for shooting feral hogs. The 7.62 is the same diameter as the .308 Winchester and the .30-06 Springfield, both of which are very popular hunting rounds In fact, all three of the .30 rounds have nearly the same power/performance/ballistics.
First confusing bit for you, much to follow: The .30-06 is .308 but the caliber is rounded down, and the -06 designates the year it was adopted by the military.
9mm – Also called 9mm Luger, 9mm Parabellum, or 9×19. numbers have same dimensional meaning as above.
Now we get into inches:
.50 calibrate – .50 caliber is .50 inches in diameter. You most commonly hear this in relation to .50 BMG (Browning Machine Gun), which is technically known by the metric 12.7×99 (notice how much bigger those numbers are than the above). It was originally designed for that machine gun, but its popular civilian use is in bolt-action or single-shot rifles.
45 ACP – This is the .45 Automatic Colt Pistol, aka .45 Auto, because that’s what it was developed for. It’s .45 caliber, or by metric 11.43x23mm.
Now here’s where it gets fun. Many of these diameter measurements are inaccurate for various historical reasons. The .223 Remington is based off the .222 Remington, a varmint round (foxes, coyotes, etc.) designed in 1950. They just stretched the case 2mm and moved the shoulder forward to increase powder volume a bit to get a few percent more velocity. They named it .223 to avoid confusion. And they’re both actually .224 diameter.
Very old cartridges often had a paper patch around the bullet so the barrel was bigger than the actual bullet. So you have the .45-70 being actually .458 in diameter, and today we use .458 bullets because we don’t use a paper patch. But it gets more confusing! That 70 does not refer to case length, but the standard charge of black powder the cartridge was designed for. This caliber-powder was the common naming convention for black powder cartridges in the 1800s.
The .30-30 is a strange exception. Originally called the .30 WCF (Winchester Center Fire), a competing maker called it the .30-30 to not use the competition’s name, with the second 30 denoting the amount of smokeless powder, using the black powder naming conventions of the day.
Then there’s the .44 Magnum, actually .429 in diameter because its grandparent cartridge (it’s based off a cartridge based off that) had the bullet diameter shrunk slightly for lubrication reasons upon request from the Russians who had commissioned it (this is in the Tsar days).
The .38 Special gets even more strange. It’s really .357 but just say the history way down involves a .38 caliber bullet in a black powder revolver, and the name stuck although the diameter didn’t. The .357 Magnum is just a .38 Special with a slightly longer case and it’s named with the correct diameter. FYI, the case is not longer to make room for more powder, but so that people couldn’t put a much higher pressure .357 cartridge in a revolver only designed for the lower pressures of the .38 Special.
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