Ammunition or ammo is the term used for expendable ordnance material used in charging firearms of all kinds; such as powder, balls, shot, shells, percussion caps, rockets, missiles, energy, etc. The purpose of ammunition is to project force against a selected target or area.
All ammo has weight in Fallout 76 like in the survival modes of Fallout: New Vegas and Fallout 4. The level of the player character determines how many and which types of ammo may appear in containers or on defeated enemies. However, there are certain types of ammo that will only appear at specific locations. There is plenty of ammo scattered throughout Appalachia, but if one has the caps and doesn't feel like venturing out to find more, the nearest trader should have what they need in stock.