

Sitting down and filling up mags is "not always an option" in a pitched firefight, and largely qualifies as an Acceptable Break from Reality. Clips were the most common way to load guns in the days of everything having an integral magazine, but nowadays they're rather rare since most everything has a detachable magazine if you are asking for a box of bullets that you will shove up the handle of a handgun, you want a magazine designed for specific weapons, so that even if the cartridges are identical between two or more guns, you'll have to unload and reload one painstaking round at a time before you can take advantage of it nevermind the question of where you're getting the empty magazines from.

These cartridges are then loaded into clips and magazines note clips feed magazines and magazines feed guns. In the real world, cartridges have a variety of different calibers, lengths and propellants based on a number of factors, including desired stopping power, target penetration, and the amount of recoil and gas pressure needed for a semiauto or automatic weapon to cycle itself (or, the other way around, prevent it from exploding in your face).

An odd phenomenon in some video games with guns in that any ammunition you pick up works with either any gun whatsoever or an entire class of guns.
