It's a semi-automatic cartridge that is a little smaller than a .380 but bigger than a .25.
9 millimeter is the caliber. IMPROVING ANSWER: A "9mm" bullet is actually .355 or .356 of an inch in diameter. So the caliber is about .36, but nobody calls it that because it would be confusing....
40 S&W cartridge, bullet diameter = .401".380 ACP cartridge, bullet diameter = .355-.356".32 ACP cartridge, bullet diameter = .311 - .312"
You will have to specify if you are referring to black powder, rim fire or center fire and the weight of the projectile
45
I do not now..EDIT: 1. *know 2. Then why did you answer? 3. Caliber is a measure of a round of ammunition by the width of the bullet or shell.