@StargateSg7 ... Re: @AC ... The cat is pretty well out of the bag already
No, you cannot get an AR-15 in 7.62 NATO.
Note: 7.62x39mm (AK-47 round) or .300BLK is available, but not 7.62 NATO
Cartridge is too big.
.50 AE may be possible, however I seriously doubt it would be a good idea to fire. .50 BMG is a much different story. You need to be more specific when you talk about the calibers that a gun will shoot. A good example... a rifle that is designed to shoot .223 Remington cannot be used to shoot 5.56 NATO. While the 5.56 NATO rifle can shoot .223 Remington. (Both rounds are extremely similar however the pressures in a 5.56 NATO are higher. )
And clearly you don't know anything about guns or gun laws.
AR-15 are semi-auto only. Not select fire, nor full auto. ;-)