Springfield M1903 A4 rifle, with telescopic sights. The old bolt.action Springfield was preferred, over the semi-automatic Garand Ml which armed most riflemen, for sniping work: rate of fire was less important than accuracy.
The basic weapon of Marine Corps infantry units after March of 1943 was the M1 rifle. The M1 is a gas-operated, clip-fed, .30 caliber, air-cooled, semi-automatic shoulder weapon.