High school Army ROTC, 1972 : M14
USMC Recruit Depot, San Diego, 1976 : first rifle - M16A1. first pistol : M1911A1
While on delayed entry - after enlisting but before being shipped to boot camp - my recruiter took a group of us out to shoot with a local USMC Reserve unit. The first gun I fired was the M2 50 cal BMG.