MR556 A4 Upper Receiver Kit – 11″

The 11-inch upper receiver kit for the MR556 A4 in 5.56×45.

What an upper receiver kit is: the complete upper half of the rifle — barrel, gas system, bolt carrier group and handguard — without a lower receiver. It lets you change calibre or barrel length on an existing lower rather than buying a second complete rifle.

Fits: MR556 A4 lower receivers. Check compatibility with your specific lower before ordering — MR-series uppers are not cross-compatible with standard AR-pattern lowers.

Worth knowing: pairing a short upper with a stocked lower creates a short-barrelled rifle, which is a regulated configuration. Understand the rules before assembling. The 16.5in kit avoids that question.

Browse the upper receiver kits range, or upper receiver parts for individual components.

Firearms and regulated components are not sold directly on this site. Listings are informational and link to the manufacturer web shop or an authorised dealer. Upper receiver rules vary by jurisdiction — confirm what applies where you live.