Precision Reflex Mk12 Mod 0 Spr Gen Ii 5.56Mm 18'' Bbl 1-8 Twist Upper Black

The Precision Reflex Mk12 Mod 0 SPR Gen II 5.56mm upper receiver is a complete, ready-to-run tactical upper built around the proven design of the U.S. Navy's Special Purpose Rifle. Pair it with any mil-spec AR-15 lower receiver and you've got a shooter that balances accuracy, reliability, and real-world usability without unnecessary complexity. This is the kind of upper that appeals to precision riflers, SPR enthusiasts, and shooters who want field-proven performance without gimmicks.

At the heart of this upper sits an 18-inch Douglas barrel made from 416 stainless steel with a 1-8 twist rate and M4-type feed ramps. The barrel is free-floated and custom-fitted to a standard commercial bolt carrier, which means you get MOA-class accuracy right out of the box. The 5.56x45mm NATO chamber handles both military and civilian .223 Remington ammunition without issue. A rifle-length gas system keeps gas velocity in check, promoting reliable operation under realistic conditions. The OPS muzzle brake helps manage recoil and muzzle rise, which is genuinely useful when you're trying to maintain sight picture during rapid engagements or precision strings.

The handguard is Precision Reflex's Gen II Retro Carbon Fiber Forend, which replicates the classic lines of the original Mk12 while delivering a full-length Picatinny rail on top for mounting optics and accessories. You also get 3-inch Picatinny segments at the 3, 6, and 9 o'clock positions up front, giving you flexibility for lights, lasers, or grips without cluttering the setup. The included PRI Gas Buster charging handle has an oversized latch that's easy to manipulate even in gloves or under stress. Flip-up sights (elevation-adjustable front, windage-adjustable rear) come installed and require no tools to deploy or stow. The entire package—barrel, brake, receiver, and forend—wears a non-reflective matte black finish.

This is a complete upper assembly, so installation is straightforward: drop it on your lower receiver and you're ready to go. It's the kind of build that works equally well at the range, in a precision rifle competition, or as the foundation of a no-nonsense patrol or duty rifle.

Key Features

• Free-floated 18" Douglas 416 stainless steel barrel for consistent accuracy
• Custom bolt carrier fitted to barrel for optimal performance
• Rifle-length gas system optimized for reliability
• OPS muzzle brake reduces recoil and muzzle rise
• Extended Picatinny rail on top; supplemental rails at 3, 6, and 9 o'clock positions
• Gen II Retro Carbon Fiber Forend with classic SPR lines
• PRI Gas Buster charging handle with oversized latch
• Tool-free flip-up iron sights (elevation front, windage rear)
• Accepts both 5.56 NATO and .223 Remington ammunition
• Matte black non-reflective finish throughout
• Fully assembled; compatible with any mil-spec AR-15 lower receiver

Specifications

Frequently Asked Questions

What lower receiver does this upper fit?

The Mk12 Mod 0 SPR Gen II upper is designed for mil-spec AR-15 lower receivers with standard .250" pivot and takedown pin holes. It uses a commercial-diameter bolt carrier, so compatibility is straightforward with any mil-spec lower.

Is this upper truly ready to shoot out of the box?

Yes. The upper arrives fully assembled with barrel, bolt carrier, charging handle, muzzle brake, handguard, and iron sights all installed. Once you mount it on a lower receiver and function-check it, you can take it to the range or field.

What accuracy should I expect?

The free-floated barrel and custom bolt-to-barrel fit are designed to deliver MOA-class accuracy. Real-world performance depends on ammunition quality, shooting conditions, and shooter skill, but the platform is built for precision work.

Can I use .223 Remington ammunition in this upper?

Yes. The 5.56x45mm NATO chamber safely accepts both military and civilian .223 Remington ammunition.