The M40 is a bolt-action sniper rifle used by the United States Marine Corps. It has had four variants — the M40, M40A1, M40A3, and M40A5. The M40 was introduced in 1966. The changeover to the A1 model was completed in the 1970s, the A3 in the 2000s, and the A5 in 2009.
Each M40 is built from a Remington 700 bolt-action rifle, and is modified by USMC 2112 (Armorers) 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 M40A5 will incorporate a detachable magazine and a threaded barrel to allow for the use of a sound suppressor or other muzzle device.
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 stocks made by McMillan, with new scopes. The trigger pull on both models (M40A1/A3) is 3 to 5 lb (2.3 kg).
During the Vietnam War, the Marine Corps decided they needed a standard sniper rifle. After testing several possibilities, they ordered 700 Remington Model 40x rifles (target/varmint version of the Model 700 bolt-action rifle), and gave them the M40 designation. Most had a Redfield 3–9 power Accurange variable scope mounted. With time, certain weaknesses, primarily warping of the all-wood stock, became apparent. Sometime in the early 1970s, the USMC armorers at MCB Quantico began rebuilding the original M40s into M40A1s. The process involved, among other improvements, replacing the original wood stocks with McMillan A1 fiberglass stocks, as well as replacing the original Redfield scopes with Unertl scopes. The M40 was originally designed by Jack Cuddy and Neill Goddard. The stock featured Wichita sling swivels and a Pachmayr buttpad.
Development of the M40A3 began in 1996, and the final product was revealed in 2001. Since then, numerous minor changes have occurred to the platform. Listed here is the latest configuration and components used in the M40A3.
Action: The M40 has always been based on the proven Remington 700 Short Action and this is no different in the M40A3. These actions are all chambered in 7.62 mm NATO and are house tuned by Marine armorers; the trigger guard assembly is manufactured by the DD Ross Company, though several M40A3s use Badger Ordnance trigger guards. In 2007, the Marine Corps began replacing the DD Ross trigger guard assemblies with the M5 detachable magazine trigger guard manufactured by Badger Ordnance.
Barrel: The barrel is a Schneider 610 24-inch, 6-groove, 1:12" match-grade heavy barrel.
Stock: All service M40A3s are based upon the A4 Tactical Riflestock, a high-quality benchrest-style fiberglass riflestock made by McMillan Fiberglass Stocks and cast molded in an OD Green color. The action is glass bedded into the stock with aluminum pillars, while the barrel is allowed to "float" (it is attached only to the action), ensuring maximum accuracy. The stock has adjustable length-of-pull (through a buttstock spacer system) and a Marine manufactured adjustable saddle-type cheekpiece. The stock also has six mount flush cups, two on each side front and back and one each on the front and rear underside. One bipod stud is located on the underside of the forearm.
Sling: The Model 1907 sling that has been historically used on M40A3s has been replaced with the Quick Cuff Model Two sling manufactured by Tactical Intervention Specialists.
Bipod: The M40A3s use a 6–9" Harris notched swivel type bipod with a KMW podlock. The QD bipod attaching screw is replaced with a screw made by Jon Tank of Tanks Rifle Shop.