7.62x51mm
The G3 rifle can chamber the 7.62x51 NATO cartridge, and it could chamber the .308 Winchester if it needed to. No other cartridges are compatible with this rifle.
a .22 caliber
A .177 caliber air rifle has very little recoil.
.223 caliber or 5.56mm.
500-600 rpm
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.
The Dragunov (note corrected spelling) sniper rifle is in caliber 7.62x54mmR. This is the same caliber at the Moisin-Nagant 91/30 rifle.
50 caliber
value of a model 49 ithaca 22 caliber rifle
You will need the services of a good gunsmith.
No