Centurion Arms MK12 Mod 1 Complete 5.56 NATO Rifle 18" Barrel - 30 Rd

Centurion Arms MK12 Mod 1 Complete 5.56 NATO Rifle 18" Barrel - 30 Rd

The Centurion Arms MK12 Mod 1 isn't chasing a legacy — it is the legacy, rebuilt from the ground up for the modern precision shooter. Where the Mod 0 defined the original SPR concept, the Mod 1 configuration refined it — evolving the platform with a cleaner, more modular handguard solution while preserving every element that made the MK12 Special Purpose Rifle one of the most effective designated marksman systems ever fielded by Naval Special Warfare.

At the heart of this build is the same 18" match-grade, air-gauged stainless steel barrel that gave the original SPR its legendary reach — a free-floating, precision-contoured tube optimized for the 77-grain Mk 262 OTM cartridge and capable of engaging targets far beyond the effective range of any standard carbine. Wrapped in a 12" Centurion C4 free-float M-LOK handguard, the barrel floats completely free of contact pressure, harmonizing cleanly with each shot for the kind of group-to-group consistency that precision roles demand. A low-profile pinned MK12 gas block keeps the profile clean and the gas system locked in place, while the OPS Inc. brake and collar stand ready to interface with suppressor systems whenever the mission calls for a quieter profile.

The Centurion Arms AST two-stage trigger delivers the refined shot control that separates a precision rifle from a general-purpose carbine, and the B5 SOPMOD stock brings the platform into the modern era — adjustable, combat-proven, and built for the realities of the field. This is the MK12 Mod 1 as it was meant to be: historically grounded, tactically current, and uncompromisingly precise.

18" Match-Grade Stainless Steel Barrel
Air-gauged for dimensional precision and Cerakoted Black for lasting corrosion resistance, this 1:7" right-hand twist barrel is purpose-built to extract maximum performance from 77-grain OTM ammunition — the same cartridge standard established by the original Navy SPR program for reaching out beyond standard carbine limitations.

12" Centurion C4 Free-Float M-LOK Handguard
The full free-float design eliminates all barrel contact, removing the vibration and pressure interference that degrade precision at distance. The M-LOK interface provides a clean, lightweight profile with unlimited modularity for lights, lasers, grips, and accessories exactly where you need them.

Centurion Arms Low-Profile Pinned MK12 Gas Block
Machined to MK12 specification and pinned securely to the barrel, this low-profile gas block maintains proper alignment and reliable function while keeping the handguard profile clean and unobstructed.

OPS Inc. Muzzle Brake and Collar
Directly replicating the original SPR muzzle device, the OPS Inc. brake delivers meaningful recoil and muzzle rise reduction while the precision-fit collar provides the correct alignment interface for the OPS Inc. 12th Model Suppressor — keeping this rifle suppressor-ready from the factory.

Chrome Sandcutter BCG with E4 Tapered Lug Bolt
Enhanced tapered lug geometry improves lockup consistency while the chrome lining ensures long-term durability and smooth, reliable cycling under sustained or suppressed fire conditions.

Centurion Arms AST Two-Stage Trigger
The Advanced Sniper Trigger provides a smooth, well-defined first stage and a crisp, repeatable break — delivering the precision shot control that designated marksman and long-range shooting applications require.

Forged Mil-Spec CM4 Upper and Lower Receivers
Both receivers are forged to mil-spec standards with Type 3 hard coat anodizing and M4 extended feed ramps, providing proven durability and enhanced feeding reliability with the full range of 5.56 NATO loads.

Specifications

• Caliber: 5.56×45mm NATO
• Barrel Length: 18 Inches
• Barrel Material: Match-Grade Stainless Steel, Air-Gauged
• Barrel Finish: Cerakote Black
• Twist Rate: 1:7" Right-Hand
• Gas System: Mid-Length
• Gas Block: Centurion Arms Low-Profile Pinned MK12 Gas Block
• Muzzle Device: OPS Inc. Muzzle Brake and Collar
• Suppressor Interface: Compatible with OPS Inc. 12th Model SPR MBS
• Handguard: 12" Centurion C4 Free-Float M-LOK Rail
• Upper Receiver: Forged Mil-Spec CM4, Type 3 Hard Coat Anodized, M4 Extended Feed Ramps
• Lower Receiver: Centurion Arms CM4 Forged
• Bolt Carrier Group: Centurion Arms Chrome Sandcutter BCG, E4 Tapered Lug Bolt
• Trigger: Centurion Arms AST Two-Stage Advanced Sniper Trigger
• Trigger Guard: Aluminum Winter Trigger Guard
• Grip: Ergo
• Stock: B5 SOPMOD
• Buffer: Carbine Length
• Optics: Not Included
• Included in Box: Rifle, (1) 30-Round Magazine, Digital USGI Manual, Centurion Arms Propaganda