The United States Navy Mark 12 Mod 0/1 Special Purpose Rifle (SPR) is a rifle in service with United States Special Operations Forces in Operation Enduring Freedom and Operation Iraqi Freedom. SPR initially stood for Special Purpose Receiver, but that nomenclature has been replaced as the weapon became a stand-alone weapons system, and not just an add-on upper receiver assembly. The SPR was eventually type classified by the U.S. Navy as the Mk 12.
The SPR, used by Special Operations Forces of both the U.S. Army and U.S. Navy, is a heavily modified light sniper/designated marksman variation of the AR-15/M16 line of infantry weapons, and is chambered for NATO standard 5.56x45mm ammunition. The SPR concept was originally proposed by Mark Westrom, currently president of ArmaLite, while working at Rock Island Arsenal. The program was an outgrowth of the desire by both US Army and Navy special operations forces for a rifle with greater effective range than an M4 carbine but still shorter in length than a standard issue M16A2/A4. The SPR program appears to have grown out of both the SOPMOD Block II program, and the U.S. Navy SEALs Recon Rifle (a 16″ flat-topped M16 carbine). The Naval Surface Warfare Center, Crane Division expanded on the Recon Rifle, an expansion that some SEALs maintain was a waste of time and resources.
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The exact history of the SPR is unclear, but there appear to be either four or five prime iterations of the weapon, culminating in the most recent Mk 12 Mod 1 version. One progression has four models: SPR Proto 1, SPR Proto 2, Mk 12 Mod 0 and Mk 12 Mod 1. The other progression has five models: SPR, SPR/A, SPR/B, Mk 12 Mod 0, and Mk 12 Mod 1. The specifications in this article follow the second progression.
Different U.S. military service branches appear to typically deploy different iterations of the SPR. Photographs, including both U.S. Department of Defense photographs and privately-obtained photographs, consistently show most U.S. Army Special Forces operators using the Mk 12 Mod 0, while NAVSPECWAR operators and U.S. Army Rangers have been identified as using the Mk 12 Mod 1 version.
The SPR has been featured prominently both in media photos of the Iraq War and in video games such as the government-created America’s Army: Special Forces and in Tom Clancy’s Ghost Recon 2.