Even very early on in its development stage, a small number of weapons were hurriedly pressed into service with the U.S. Navy SEALs deployed to Southeast Asia. During 1967, the Stoner 63A system was field tested by Company L (Lima Company), 3rd Battalion, 1st Marine Regiment, 1st Marine Division. Riflemen were issued the weapon in the Rifle configuration (in both 63 and 63A variants, designated XM22 and XM22E1 respectively), while officers and certain other personnel received the Carbine (XM23). The Automatic Rifle configuration was deployed on a limited basis in the squad automatic role, while Lima's weapons platoon received both the LMG and MMG configurations.