The M40 is a bolt-action sniper rifle used by the United States Marine Corps. It has had three variants — the M40, the M40A1 and the M40A3. The M40 was introduced in 1966. The changeover to the A1 model was completed in the 1970s, and the A3 in the 2000s. Each firearm begins life as a Remington 700, and is then extensively modified by hand by USMC 2112/gunsmiths at Marine Corps Base Quantico, using components from a number of suppliers. New M40A3s are being built, and A1s are upgraded to A3s as they rotate into the armory for service and repair. The rifles have had many sub-variations in telescopic sights, and smaller user modifications.
The original M40 was a military type-classified version of the Remington 700; it was factory-made, and had a one-piece wooden stock. The M40A1 and A3 switched to fiberglass, with new scopes added as well. The trigger pull on both models (M40A1/A3) is 3 to 5 lbs. [wikipedia]