The correct size of the bullet that fits the rifle.
Depends on the application. If you mean power, the higher the caliber, the more powerful it is. for example, a .22 caliber rifle is much less powerful than a .50 caliber rifle.
It's the caliber of the cartridge it fires.
You will have to me more specific. Do you mean any rifle that fires a 30 caliber projectile or 30/06 or 308?
Usually caliber and/or serial numbers.
you will have to define if you mean commercial or wildcat.
a .22 caliber
If you mean the jacket, it all depends on the caliber and maker.
A .177 caliber air rifle has very little recoil.
.223 caliber or 5.56mm.
No You could build a rifle in .306" or any other caliber but you are likely referring to 30.06. A 30.06 rifle is referred to as "30 Caliber" but to be accurate it is nominally .308"
Yes, I can. A Barrett M107 is a .50 caliber sniper rifle.
Well, it depends on what you mean. The caliber is "determined" at time of production based on whatever caliber the manufacturer wants it to be. The caliber can be determined later by looking on the barrel. The caliber will almost always be stamped somewhere on the barrel.