What type of headspace does the M249 automatic rifle feature?

The M249 automatic rifle features a fixed headspace. Fixed headspace refers to a design where the distance between the bolt face and the chamber is established at the factory and cannot be adjusted during normal use. This design ensures that the rifle operates reliably and consistently, as the headspace remains within specified tolerances that suit the ammunition being used.

Having fixed headspace helps avoid complications that can arise from adjustable systems, such as the need for continuous monitoring and adjustment by the operator, which can sometimes lead to errors or malfunctions. A fixed design also tends to enhance reliability in adverse conditions, which is critical for military firearms. This is particularly important for the M249, which is deployed in various environments and must maintain optimal performance regardless of the circumstances.