The SR-25 (Mk 11) in United States Marine Corps is a designated marksman rifle designed by Eugene Stoner and manufactured by Knight’s Armament Company.
The SR-25 uses a rotating bolt and a direct impingement gas system. It is loosely based on Stoner’s AR-10, rebuilt in its original 7.62×51mm NATO caliber. SR-25 barrels were originally manufactured by Remington Arms with its 5R (5 grooves, right twist) rifling, with twist 1:11.25. The heavy 20-inch (510 mm) barrel is free-floating, so handguards are attached to the front of the receiver and do not touch the barrel.
In 2005, a modified version of the SR-25 / Mk 11 rifle won US Army Semi-Automatic Sniper Rifle (XM110 SASR) competition, and today it is being issued to US Army snipers as the M110 Semi-Automatic Sniper System.
The SR-25 enhanced match rifle utilizes the newer URX II Picatinny-Weaver rail system, rather than the older Mk 11 free-floating RAS, on the top of the receiver to accept different scope mounts or a carrying handle with iron sights (front sight mounted on the rail located on the forward end of the non-modular handguard). The match version is designed to shoot at a precision of 0.5 minutes of angle, which corresponds to 0.5-inch (13 mm) groups at 100 yards (91 m).
The Mk 11 Mod 0 system is chambered for 7.62×51mm NATO and is designed for match-grade ammunition. The Mk 11 system includes the rifle, 20 round box magazines, QD (Quick Detachable) scope rings, Leupold Mark 4 Mil-dot riflescope, Harris swivel-base bipod on a Knight’s mount, and QD sound suppressor, which is also manufactured by Knight’s Armament Co. Flip-up BUIS (Back up iron sights) are attached to the modified gas block and upper receiver.
The Mk 11 Mod 0 utilizes an Obermeyer 20 in (510 mm) match target barrel, along with a RAS (Rail Accessory System) fore-end made by KAC, consisting of an 11.35 in (288 mm) long match fore-end. The RAS allows for quick attachment/detachment of MIL-STD-1913 components. The aluminum fore-end makes no contact with the barrel forward of the receiver, allowing for extreme accuracy. The Mk 11 Mod 0 has an empty weight of 15.3 lb (6.9 kg), and an overall length of 45.4 in (115 cm). The civilian version, using the longer 24 in (610 mm) match barrel, is guaranteed to produce groupings of less than 1 in (25 mm) at 100 yd (91 m), or 0.3 angular mil, using factory match loads.
During the Iraq War, the United States Marine Corps ordered 180 Mk 11 Mod 1 rifles. These were Mk 11s equipped with the upper receiver of the M110 Semi-Automatic Sniper System. The M110 upper gave the Mk 11 Mod 1 a URX modular rail system and a flash suppressor on the barrel. These saw limited use before they were phased out when the Marines chose to purchase the Mk 11 Mod 2, which was simply the USSOCOM and U.S. Navy designation for the complete M110 rifle.
The new SR-25 Enhanced Match (E.M.) Carbine is very similar to the KAC M110 Semi-Automatic Sniper System, though the M110 utilizes the newer URX Rail system, a length-adjustable fixed buttstock, and an integrated flash suppressor. Starting late 2011, USMC snipers will replace Mk 11 Mod 0 rifles with the M110 on a one-for-one basis.
|Mass||Match Rifle 10.75 lb (4.88 kg),
LwMatch 9.5 lb (4.3 kg),
Carbine 7.5 lb (3.4 kg),
Sporter 8.75 lb (3.97 kg)
|Length||1,118 mm (44.0 in)|
|Barrel length||Match Rifle 24 in (610 mm)|
|Action||Gas-operated, rotating bolt|
|Rate of fire||Semi-automatic|
|Feed system||10 and 20-round detachable box magazine|