| ||For an overview of 5mm round in the Fallout series of games, see 5mm round.|
5mm is traditionally belt-fed, and is available in rather high quantities, something made necessary by the notably large "magazine" sizes on the weapons that use it—for example, the minigun loads 240 rounds at one time and fires an exceptional rate, meaning to be used effectively large amounts are often required.
- Generally speaking, the 5mm round is the most common big guns ammunition found in the game, as super mutants- especially brutes and masters- tend to favor the minigun. Members of the Brotherhood of Steel tend to carry miniguns as well, and with their alarming death rate outside GNR building plaza, it's possible to get some 5mm rounds here as well.
- Lucky Harith carries this ammunition (up to 1000 rounds) when fully invested in.
- They are abundant throughout the add-on The Pitt.
- In The Pitt, 5mm rounds can be used easily to make other ammunition types in the ammo press due to their abundance.
- When dropped, 5mm rounds have the largest containers.