When people talk of guns, they often refer to them by the action the gun uses to prepare the next round to fire.
For centuries, all guns were single shot weapons. You’d fire once and then have to reload. If you wanted to fire more than once, you needed to add another barrel.
Until the metal cartridge came along, all guns were muzzle loaders. That means that the powder and bullet were shoved down the front of the barrel. The “primer” may have been a piece of flint, or a burning string that the shooter placed in the flash hole by hand, or it may be a modern percussion cap that ignites the charge. These guns are still called by the method of ignition used: Matchlock, Flintlock, Cap and Ball, and so on.
Other types of single shot actions are:
