There are numerous handguns that will fire more than one caliber or type of ammo. The Taurus Judge will fire .410 shotgun ammo or .45 Colt ammo. Smith and Wesson has just started producing a gun similar revolver called the Governer that will fire .410, .45 Colt, or .45 ACP.
You can fire .38 special in any gun that is chambered in .357 magnum (but not vice-versa) or .44 special in a gun chambered for .44 magnum (but not vice-versa).
Also there are other types. There is a very rare revolver called the Medusa that will fire anything in the .38 or 9mm family, including 9mm Kurz (380), 9x19mm, 38 special, and .357 magnum.
.22
Look on the barrel, it will be marked as to the proper ammunition.
It should be marked on the barrel
It depends on what you mean. Handgun magazines don't fit handguns based on size, they fit based on which model you have. Some models of pistol have various capacity magazines...for instance, for a Sig 229 in 9mm, you can get 10 round magazines and 15 round magazines.
Everything in the proper gauge/size.
The ak 74 fires 5.45x39 caliber ammunition.
Remington makes a variety of rifles and shotguns using various sizes of ammunition.
There is no way we can answer your question without more information. There are guns such as the Flobert actions that cannot safely fire any ammo but the .22CB cap (smaller than a short, no powder, primer only) and others that can fire .22 Short, Long, or Long Rifle interchangeably. I have one .22 revolver simply marked .22 RF- it predates the .22 LR cartridge. We would urge you not to attempt to fire ANY ammunition until your handgun has been checked by a competent gunsmith to determine the correct ammo, and if it is safe to fire.
45 has the larger projectile. Size of the handgun will vary.
45 = .451 9mm = .355 The .45 handgun throws the bigger and heavier bullet. The 9mm fires a lighter and smaller bullet, but at a higher speed. The size of the guns that fire either of these rounds could be the same size. Both 9mm pistols and .45 pistols come in full sized guns, compact guns, and even sub-compact or micro sized.
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