PHB p221: Ammunition: Arrows come in a quiver that holds thirty, crossbow bolts come in a case that holds twenty, and sling bullets come in a pouch that holds twenty. Ammunition is used up when you fire it from a projectile weapon.
PHB p232: Ammunition: Ranged weapons such as bows, crossbows, and slings impart their magic to appropriate ammunition fired from them. Ammunition (such as arrows, bolts, or sling stones) doesn’t come in magical versions. You can’t craft (or find) a +1 flameburst arrow or a +3 sling stone.