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Rainier Arms MK12 .223 Wylde Rifle - 18"

AR-15 Rifle

In stock
Only 1 left

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 the "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.

Our version of the MK12 features Rainier Arms Receiver Set and our Ultramatch MOD 2 barrel. Also features Precision Reflex Inc free float handguard and G1 Flip Up Front Sight with a .750 Crossbolt.

Upper Build:

  • Rainier Arms Forged Upper Receiver
  • Rainier Arms Ultramatch MOD2 .223 Wylde SPR Barrel - 18"
  • Precision Reflex Inc Gen III AR15/M16 Rifle Length Round Carbon Fiber Free Float Handguard - 12.5 " Black
  • Precision Reflex Inc G1 Flip Up Front Sight with .750 Crossbolt
  • A2 Flash Hider 

Lower Build:

  • Rainier Arms Forged Lower Receiver
  • Rainier Arms AR-15 Precision Match Grade BCG - Nitride
  • Rainier Arms Modified Trigger Guard - Black
  • ALG Defense Quality Mil-Spec Trigger
  • B5 Systems Steel End Plate - Black
  • B5 Systems Type 23 P-Grip - Black
  • B5 Systems Enhanced SOPMOD Stock - Black
  • VLTOR AR15 Charging Handle - Medium Latch

Weight: 7 lbs 13 oz

More Information
SKU RA-MK12-DI-223-18-R
Product Type AR-15 Rifle
Manufacturer Rainier Arms, LLC
Gas Block Diameter .750"
Thread Pitch 1/2x28
Twist Rate 1:7.5
Color Black
Gas Length Rifle
Rail Length 12.5"
Barrel Length 18"
Caliber .223 Wylde

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