Heckler and Koch (HK USA) | MR764A4 URK | 7.62 x 51mm | 308 Win | Matte Black

HK's MR764A4 Upper Receiver Kit brings the same short‑stroke gas piston system used across the MR‑series to a 7.62x51mm upper, letting an existing compatible AR‑10‑pattern lower run HK's closed‑gas engineering without buying a complete rifle. The closed‑gas system keeps hot carbon fouling and waste gas out of the receiver entirely, and a cold hammer‑forged barrel with an adjustable gas regulator lets you tune the action for suppressed or unsuppressed fire. Real HK416/​MR762‑pattern .308 engineering as a drop‑on upgrade rather than a full rifle purchase.