The United States Navy Mk 12 MOD 0/1/H Special Purpose Rifle (SPR) is a designated marksman rifle that was in service with United States Special Operations Forces in the designated marksman role until 2017, also designed to be shorter than standard weapons. SPR initially stood for Special Purpose Receiver as it referred to an add-on upper receiver assembly (part of the proposed SOPMOD upgrades), but that nomenclature changed to Special Purpose Rifle as the weapon became a stand-alone weapons system.
The SPR was eventually type-classified by the U.S. Navy as the Mk 12.
The Mk 12 was developed to bridge the gap between standard infantry rifles such as the M4 carbine and larger sniper systems like the SR-25, offering improved accuracy and effective range while maintaining relatively low weight and maneuverability.
The system was designed to provide increased precision at extended ranges compared to standard service rifles while remaining lighter and more maneuverable than traditional sniper platforms.
The SPR concept was originally proposed by Mark Westrom, president of ArmaLite, while working at Rock Island Arsenal in 2000. Its design group included John Noveske and Steve Holland. They were mostly deployed as designated marksman rifles (DMR).
The Mk 12 was phased out of service in 2017.
Design
Upper receiver
The majority of the SPR upper receivers were initially supplied by Colt, with others being produced by Diemaco (now Colt Canada).
The barrels are manufactured by Douglas Barrels with a unique contour that reduced weight but maintained rigidity for accuracy. An OPS Inc. muzzle brake and collar (to align the OPS Inc. 12th Model Suppressor) is installed with the barrel.
A long accessory rail, called a Swan Sleeve (ARMS SPR MOD or ARMS #38 SPR PEQ-2-3), manufactured by ARMS, is installed, running the length of the rifle.
In 2014, Ops, Inc stopped manufacturing this model of suppressors. The equivalent product is currently manufactured by Allen Engineering Co as the AEM5. The AEM5 is essentially the same suppressor design and actually built by the same individual, Ron Allen, who previously fabricated the 12th model suppressor for Ops, Inc.
Ammunition
The SPR is not used to fire standard issue 5.56mm M855A1, M193 ball, or M856 tracer ammunition.
Black Hills then approached the Nosler bullet manufacturing company, who made a similar OTM bullet, and Nosler agreed to supply cannelured bullets to Black Hills.
The newer load was designated Mk 262 MOD 1. Recently, Sierra added a minimal cannelure to its bullet, and this has since replaced the Nosler bullet in the current versions of Mk 262 MOD 1. In late 2014, Sierra introduced a tipped version of this bullet which adds a polymer tip to improve ballistics.
This new bullet was found exclusively in an upgraded version of the Black Hills Ammo MK262 MOD 1 loading, but this bullet has been released by Sierra to reloaders prior to the end of 2014. The Sierra part number for this bullet is 7177.
Clones
The Mk 12 SPR has been manufactured by various firearms companies as clone rifles after the Mk 12 was phased out.
Centurion Arms manufactures clones of the Mk 12. Troy Industries made a retro Mk 12 for sale in 2017. Oberland Arms released a version of the Mk 12 in 2019.
Palmetto State Armory released clones of the Mk 12 Mod 0, Mod 1, and Mod H in 2023 known as the Sabre Mk 12. Precision Reflex Inc unveiled a Mk 12 rifle chambered in .308 Winchester in SHOT SHOW 24 in January 2024.
Gallery
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File:USMC-081005-M-4507D-005.jpg|Mk 12 Mod 1 with visible markings
Image:Mk12223.jpg|US Army SF takes aim with his desert camouflage-painted SPR. An Insight Technologies AN/PEQ-2A Target Pointer/Illuminator Aiming Light (TIPAL) is mounted on the right of the rifle's handguards. A standard M4 telescoping stock is mounted.
Image:Mk12_Mod0_Profile.jpg|An SPR, not a Mk 12 Mod 0. Note the early PRI freefloat tube of constant diameter. This SPR has a Versa-pod bipod and has a fixed stock. The upper receiver has a teardrop-shaped forward assist.
Image:US Navy 070907-N-6477M-113 A U.S. Special Forces Soldier conducts rehearsal, training and pre-operation conformation on the MK 12 sniper rifle.jpg|A U.S sniper looks through the scope of a Mk 12 Mod 1 Special Purpose Rifle.
File:Defense.gov News Photo 101101-M-6340O-058 - U.S. Marine Corps Lance Cpl. Steven J. Zandstra provides security at a checkpoint in Sangin Helmand province Afghanistan on Nov. 1 2010.jpg|Mk 12 Mod 1 rifle in USMC service in Afghanistan, 2010.
File:USMC-090509-M-9706A-177.jpg|A USMC Mk 12 Mod 1 on a range in Iraq.
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