The MR762 upper receiver kit has been updated to include all the new A4 features, including new barrel profile, adjustable gas block, handguard and more. This kit includes a complete upper receiver/barrel assembly, allowing Mil-Spec 7.62 mm AR-style rifles to be retrofitted to HK’s piston and pusher rod system. This system utilizes a piston and a pusher rod in place of the gas tube normally found in AR15/M16/M4-style rifles. This closed system virtually eliminates the malfunctions that are common in direct-impingement gas systems, since hot carbon fouling and waste gasses are not propelled into the receiver area to operate the action. This is the same key feature critical to the success of the HK417 used by elite military and law enforcement customers. The MR762 A4 is assembled in the USA using US and German-made components and uses many of the same parts and assemblies originally developed for the HK417. It functions reliably and shoots accurately with a wide variety of quality 7.62 mm or .308 ammunition. The MR762 A4 Upper kit includes: 1. Complete MR762 upper receiver/barrel assembly. barrel, upper receiver with forward assist, extended charging handle and free-floating slimline handguard. 2. Complete MR762 bolt group assembly 3. HK proprietary buffer and action spring Due to the shortened length of the HK buffer and action spring, these parts do not work in fixed-stock AR/M16 – type rifles. Installation of Mil-Spec hammers on non-HK lower receivers is required for reliable function.
