What gun is used to shoot ra 43 bullets?

All that mean is that Remington Arms manufactured the round in 1943. Since that was during WWII, you most likely have a .45 ACP (11.65x23mm), .30 Carbine (7.62x33), .30-06 (7.62x61), or .50 BMG (12.7x99) round. Production of non-military ammo was very limited during this time.