THE M240G MACHINEGUNNER MCI 0321B1. Purpose. The subject course has been published to provide instruction to all Marines. The M240G medium machinegun is found in units throughout the Marine Corps. It is likely most Marines will either use this weapon or supervise its use.2. Scope. This course addresses the operation and care of the M240G medium machinegun and its associated equipment, including the following; capabilities, maintenance, operation, basic marksmanship, troubleshooting, and night/low visibility operation.