HECKLER AND KOCH (HK USA) MR762A4 UPPER KIT 7.62MM 16″

Description

The MR762A4 upper receiver kit is built for shooters who want to run a proven battle-rifle platform on an existing MR762 lower — whether that means replacing a worn assembly, building a dedicated configuration, or upgrading to the longer barrel profile. It is a complete, drop-in assembly: upper receiver with forward assist, cold-hammer forged barrel, extended convertible charging handle, HK Free Floating Rail System handguard, full bolt group, tungsten-filled proprietary buffer, and action spring are all included. Nothing is left to source separately.

The gas system on this upper routes waste gas to operate a piston-driven action rather than directing it back into the receiver. That separation keeps hot carbon fouling out of the bolt carrier group, which reduces the heat and debris the action cycles through under sustained fire and simplifies cleaning compared to direct-impingement designs. The same architecture powers the HK417, and the MR762 shares its core operating principle with that platform. The adjustable gas block lets the shooter tune dwell time to match suppressed or unsuppressed use and a range of ammunition pressures without swapping components.

The 1-in-7-inch twist rate stabilizes heavier .308/7.62 NATO projectiles effectively — long-for-caliber bullets above 168 grains will stabilize reliably, which matters if the shooter intends to use match or precision ammunition. Lighter 147-grain loads also run without issue, so the barrel is not optimized narrowly for one niche. The cold-hammer forging process produces a bore with consistent dimensions and work-hardened steel, which holds up to extended use better than button-rifled alternatives. This kit ships in an HK soft case and is compatible exclusively with MR762 lowers.