Heckler & Koch MR556 A4 5.56 NATO Complete Upper Receiver Kit - 16"

The Heckler & Koch MR556 A4 Complete Upper Receiver Kit is a 5.56 NATO assembly designed to retrofit standard AR-style rifles with HK’s short-stroke gas piston system. The kit includes a 16.5-inch cold hammer forged barrel, complete upper receiver with forward assist, and an extended convertible charging handle. The HK Free Floating Rail System handguard provides a stable mounting platform while reducing barrel deflection. This upper incorporates the same pusher rod operating system found in the HK416, reducing carbon buildup in the action and improving long-term reliability. Also included are a complete MR556 bolt carrier group, proprietary buffer system, adjustable gas block, and soft transport case.

Features:

• 5.56 NATO complete upper
• 16.5" cold hammer forged barrel
• Short-stroke gas piston system minimizes fouling
• HK Free Floating Rail System handguard
• Complete MR556 bolt group included
• Extended convertible charging handle
• HK proprietary tungsten-filled buffer and buffer spring
• Adjustable gas block for suppressed or unsuppressed use