What distinguishes the MK-48 as a fully automatic machine gun?

The MK-48 is distinguished as a fully automatic machine gun primarily because it fires from the open bolt position. This design feature allows for better heat dissipation during sustained fire, making it more reliable in combat situations. When firing from an open bolt, the bolt remains in the rear position until the trigger is pulled, allowing a round to enter the chamber just before firing. This mechanism contributes to the rate of fire and reduces the risk of cook-off, which is a situation where a chambered round could fire due to overheating.

While aspects such as being magazine-fed and having a lightweight design may enhance its functionality and usability, they do not exclusively define it as a fully automatic weapon. The closed bolt operation is typically associated with precision and semi-automatic fire functions, which contrasts with the open bolt operation relevant to the MK-48. Thus, the open bolt firing mechanism is a critical element that characterizes the MK-48's design and operational capabilities as a fully automatic machine gun.