--Centurion Arms 18in MK12 5.56mm stainless match air gauged barrel with 1 in 7" twist (machined stainless finish)
--Upper receiver is a standard forged Mil-Spec with M4 extended feed ramps
--Centurion Arms low profile MK12 gas block, pinned
--12" Centurion Arms C4 Quad Rail
--OPS Inc. Brake and Collar
--Polished Feed Ramps
**Options Available for Mod 1, Mod 0, Mod H and Customized Uppers**
Further Information on the Original United States Navy Mark 12 Mod 0 and Mod 1 Special Purpose Rifle (SPR)
The MK12 rifle was one of the beginning stages of "enhanced carbine" concept. The original designation as SPR was intended to mean Special Purpose Receiver but the system was eventually type classified by the Navy as a standalone rifle and designated MK12 Mod 0/.1. The concept started with the idea of having a sniper/designated marksman upper receiver for a special operator's standard M4 lower receiver but during initial testing and limited fielding Naval Surface Warfare Center, Crane Division delivered the upper receiver with their own lower so the testing units would not have to deplete the units operational weapons to support the testing. The lowers supplied were mostly M-16A1 lowers with Knights Armament match triggers installed and fixed butt stocks.
Use a standard Mil-Spec type 3 hard coat anodizing. The receivers have M4 style lowered feed ramps built in to enhance reliability as well as the rail interface numbering system on top
An 18-inch, threaded muzzle, match-grade, free floating, stainless steel, heavy barrel with a 1:7 rifling twist is a standard for the SPR. The barrels are manufactured with a special contour to maximize accuracy and to minimize weight. An OPS in. muzzle and collar (to align the OPS Inc. 12th Model Suppressor) is installed with the barrel. These barrels were designed to take advantage of the new Mk 262 cartridge, which uses a 77-grain bullet.
A free-floating forearm is used, which does not touch the barrel directly. This increases the accuracy of the weapon by removing vibration and pressure exerted on the barrel by the rest of the gun. The Mk12 Mod1 uses the Knights Armament Company (KAC) M4 Match Free-Floating RAS (Rail Adapter System). The Mk12 Mod0 uses the PRI Gen III Handguard, and the addition of the PRI SPR Straight Top Rail.
Mk12 Mod1 uses the KAC rail forend flip-up front sight and the KAC 600 meter flip-up rear.
Mk12 Mod0 uses the PRI flip-up front sight (in place of standard MK12 gas block) and the ARMS, Inc #40 flip-up rear.
Current MK12 rifles are being fielded with Night Force 2.5x10 scopes and high rings.
The OPS Inc. 12th Model SPR Muzzle Brake Suppressor (MBS) threads directly onto the OPS Inc. muzzle brake and uses the collar to stay centered.
The SPR is not used to fire standard issue 5.56 x 45mm NATO M855 ball or M856 tracer ammunition and especially not M193 ball ammunition. Due to the limits in terminal performance and relatively poor accuracy of the 62-grain M855 ball, the Mk 262 Open Tip Match (OTM) round was developed as a more accurate round for the SPR, and is manufactured by Black Hills Ammunition.