The M16A2 Buttstock is about five/eight" of an inch longer then the earlier types. Because of the greater duration it applied an extended buttstock screw plus a spacer. The swivel is mounted nearer on the buttplate. This buttstock is currently employed to the M16A4: The barrel can be a 1970's https://coltpython6forsale89999.nico-wiki.com/1055352/helping_the_others_realize_the_advantages_of_colt_m16a1_for_sale