An AR-15 is a rifle that uses 5.56 mm bullets. It is a semi-automatic rifle. This specific type of bullet is the most commonly used bullet amongst the NATO forces.
It fires a 4.6x30mm cartridge.
32 auto
Ruby shot Oswald with a .38 revolver. Not much online as to the exact type of ammunition...
100-1000 USD
Carrying ammunition.
Look on the barrel, it will be marked with the correct ammunition.
Any Winchester 308 ammunition will work for you.
Ammunition shelf's were where the soldiers kept their ammunition and guns.
Shotgun shells
Most AR-type rifles are chambered for the 5.56x45 cartridge - the standard cartridge used by NATO (and also by several non-NATO) forces for their military's assault rifles. They can also chamber the .223 Remington cartridge, although a firearm with a dedicated .223 Remington chamber should not be used for military 5.56x45 ammunition.
Have it examined by a gunsmith
7.62x 39mm