HK MR762 A4 Upper Receiver Kit - 13"

The HK MR762 A4 Upper Receiver Kit is a complete 7.62×51 NATO upper assembly designed for compatibility with Mil-Spec AR-style lower receivers chambered in 7.62 mm. This kit features a 13-inch cold hammer forged barrel, HK free-floating rail system, and a short-stroke piston operating system.

The piston and pusher rod design replaces the traditional direct-impingement gas tube found in standard AR platforms. By keeping propellant gases forward of the receiver, this system is designed to reduce heat and carbon buildup within the action, supporting consistent operation during extended use.

The assembly includes an upper receiver with forward assist, an extended convertible charging handle, an adjustable gas block, and HK proprietary recoil components. All components are factory-matched and ship housed in an HK soft case.

Specifications

• Caliber: 7.62 × 51 mm NATO
• Barrel Length: 13 inches
• Operating System: Short-stroke piston
• Barrel Type: Cold hammer forged
• Gas System: Adjustable gas block
• Bolt Carrier Group: Complete MR556 bolt group assembly
• Buffer: Tungsten-filled HK proprietary buffer
• Width: 3.07 inches
• Height: 2.68 inches