I think it looks great, very well-executed. I only have two nitpicks:
I have never, in ALL of the zillions of photos I've seen of US Marines in Vietnam, seen any of them with an M16/XM148 combo (the grenade launcher), or an XM 177E2 "CAR-15". This includes photos of recon Marines. Marines tended, then and to a large extent today, to get new stuff last. Accordingly, relatively "experimental" weapons (hence the XM designations on both weapons) were rarely, if ever, tried out with them. Go with standard M16 or M16A1 configurations there, along with M79s, M60s, and the occasional M14.....likewise, the 30 round magazines (as depicted in the hands of the guy with the CAR-15) were normally only found in the hands of special forces troops like US Army Special Forces, Navy Seals, LRRPs/Rangers, and MACVSOG, and then rarely.