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Centurion Arms MK12 5.56 NATO AR-15 Rifle - 18"

AR-15 Rifle

Out of stock

FFL Required Before Shipping.

Please have your dealer email a copy of their FFL to [email protected] or fax it to 253-218-2998, referencing your name and order number.


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.


  • Centurion Arms 18" MK12 5.56mm stainless match air gauged barrel with 1 in 7" twist (blasted stainless finish)
  • Upper receiver is a standard forged Mil-Spec with M4 extended feed ramps
  • Centurion Arms low profile MK12 gas block, pinned
  • Rail: 12" Centurion Arms C4 Rail
  • OPS Inc Brake and Collar
  • BCG: Full Auto machined from MIL-SPEC Carpenter 158 Steel. MPI (Magnetic Particle Inspected), Shot Peened, Tool Steel Extractor w/enhanced extractor spring, Chrome Lined Carrier, Hardened, Chrome Lined Gas Key w/staked Grade
  • 8 Fasteners as per MIL-SPEC
  • Standard Charging Handle
  • Centurion Arms CM4 Forged Lower Receiver
  • Receiver Plate-Standard
  • Trigger: Centurion Arms 2-Stage Advanced Sniper Trigger (AST)
  • Trigger Guard: Aluminum Winter Trigger Guard
  • Buffer: Rifle
  • Grip: A2
  • Stock: A2 Standard


  • (1) Rifle
  • (1) 30rd Magazine
  • (1) Digital USGI Manual
  • (1) Centurion Arms Propaganda

Please NOTE: 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.

More Information
Product Type AR-15 Rifle
Manufacturer Centurion Arms
Twist Rate 1:7
Color Black
Rail Length 12"
Mount Picatinny
Barrel Length 18"
Caliber 5.56 NATO

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