Different machine gun bullet types like AP and HE or maybe tracers and there would be a cooldown when you switch between the ammo types and during the cooldown maybe there could be a little animation showing the character changing the belts and there could be a visual difference with the bullet types like HE is a little shorter than AP and has a orange cap while AP is longer and skinnier than HE and has a red cap and the tracers could be a mix of both and would have a green cap and the color for the types of bullets would be the same color as the cap