Operators Safety & Instruction Manual

Function of the Diemaco MRR

Your Diemaco firearm has a semi-automatic action with the following operation. With a loaded magazine

inserted and the fire control selector set to [R], the charging handle is used to cock the action and chamber

a round. When the trigger is squeezed, the trigger rotates, disengaging the trigger sear surface from the

hammer. The hammer spring drives the hammer forward to strike the firing pin. The firing pin strikes the

primer at the base of the cartridge, igniting the primer composition, which ignites the main powder charge.

High pressure gases push the bullet down the barrel where rifling grooves impart a stabilizing spin to the

bullet. As the bullet passes the gas port (a small hole in the barrel), gas is tapped off and flows through

the gas tube into the bolt carrier chamber, driving the bolt carrier rearward. As the bolt carrier moves to the

rear, the firing pin is withdrawn into the bolt, while the cam track in the bolt carrier acts upon the bolt cam

pin, causing the bolt to rotate until its locking lugs are no longer in engagement with the lugs of the barrel

extension. The bolt is now unlocked and is carried rearward by the bolt carrier.

The extractor holds the base of the spent casing against the face of the bolt, extracting it from the chamber

as the bolt travels rearward. Once the spent casing is free of the chamber and exposed to the ejection port,

the ejector then ejects the spent casing.

The bolt carrier continues rearward, compressing the return spring and returning the hammer to its cocked-

position. Rearward motion stops when the buffer assembly strikes the bottom of the receiver extension.

As the bolt moves forward, the bolt feed lugs strip the next round of ammunition from the magazine and

direct it forward into the chamber. The hammer is caught and held rearward by the disconnect.

17274S-EN