Randomizer

Hi, I recently made a ranged weapon that I want to randomly shoot different bullets, my problem is this. I want the gun to shoot one of the ammo types that the player currently has in their inventory, only one. Everytime I try this, it either consumes 3 ammo and shoots 1 projectile, or only shoots one of the ammo types then moves the next when the first runs out. It's really weird and I could really use some help