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. This weight can be reduced with the appropriate perks which will reduce the weight of a particular type of ammo. 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, it can be purchased from both traders and ammunition vending machines. Ammo can also be crafted at a tinker's workbench with the appropriate materials.
Some types of ammunition can also be enhanced with ultracite. This makes it more deadly against enemies affected by the Scorched Plague. Ultracite ammunition can only be used by weapons which have been modified with a prime receiver.