[3] Each M40 is built from a Remington Model 700 bolt-action rifle, and is modified by USMC armorers at Marine Corps Base Quantico, using components from a number of suppliers.

The M40A5 incorporates a detachable magazine and a threaded barrel to allow for the use of a sound suppressor or another 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.

[5] During the Vietnam War, the Marine Corps decided they needed a standard sniper rifle.

[6][7] The Marine Corps eventually decided to continue upgrading the M40A-series and keep the 7.62 NATO round, primarily due to the higher cost of larger rounds and scout sniper training that can achieve kills beyond the weapon's effective range.

[9] These actions are tuned by Marine armorers; the M40A1 trigger guard and floor plate was assembly manufactured by Winchester using the model 70 steel which was cut about one inch to fit the Remington 700 action and McMillan camo stock.

[10] Dayscope: The M8541 Scout Sniper Day Scope is a Schmidt and Bender Police Marksman II LP 3–12×50 modified by Premier Reticles.

[4] The standard front ring cap is replaced with a SPA-Defense B634 34mm Male Dovetail, as a mounting platform for the Simrad KN200 Night Vision Weapon Sight.

[12] All M40A5s are fitted with a Badger Ordnance detachable magazine system and a forward rail mount for the AN/PVS-22 night vision optic.

Upgraded features are to include a folding stock, compatible with current M40 actions and barrels, to make the rifle more compact for transportation inside confined spaces like vehicles and a full-length rail to accommodate optics and accessories; the M40A5 has only a few inches of rail space beyond the scope for a night vision optic, so extending the rail length would allow more accessories to be attached, enabling snipers to put rounds on target under any conditions.

Deliveries were to begin three months after the contract being awarded, with 1,100 stocks to be purchased to upgrade the entire M40A5 inventory.

[1] The primary difference between the Army and the U.S. Marine Corps rifles is that while the U.S. Marine Corps M40 variants use the short-action version of the Remington 700/40x which is designed for cartridges having an overall length of 2.750 inches (69.85 mm) or less (such as the .308 Winchester/7.62×51 mm NATO), the Army M24 uses the Remington 700 Long Action.

[17] Despite the fact that the M24 came fitted with a 7.62×51 mm NATO barrel upon issue, retaining the longer action allowed them to reconfigure the rifle in dimensionally larger cartridge chamberings if necessary (which has been the case during the longer engagement distances during Operation Enduring Freedom).