@Cucoo
Well, I would say that the gun that best matches would be an FN Five Seven.

It has a 20 round clip and uses 5.7×28mm rounds. It's not fully-automatic, but you could say that it's modified to go into full-auto.
As for the revolvers, there are different sizes of pistols and revolvers.
I believe that the most common pistol ammo calibers are .22, 9mm, 10mm, .40, .45, and .50. There's many other types, but those seem to be the most basic.
Revolvers have the .22 Long rifle, 9mm Luger Parabellum, .357 Magnum, .40 S&W, .45 ACP, .44 Magnum, and .50 AE (Action Express).
Here's the revolver rounds.
