In the jungles of Vietnam, US special forces started to deploy under-barrel grenade launchers with the philosophy of combining grenadier and rifleman “seamlessly” into one platform. Beginning development in 1964 with the GLAD project (Grenade Launcher Attachment Development), MACV-SOG (Military Assistance Command, Vietnam-Studies, and Observation Group) operators were finally slung in 1967 with the XM148 grenade launchers under their XM177 carbines, the progenitors of the Colt Commando, M4 series, and arguably, the AKS-74U “Krinkov.” Just a year later, the US was fielding to great effect full-size M16s with the pump open XM203, instantly recognizable by its distinct cheese grater ventilated heat shield over the rifle’s barrel. Soviet intelligence quickly took notice of this development cycle, likely long before the weapon ended up in the hands of US operators.