Well, I "sorta" carried an M16 in Viet Nam. Actually it was a CAR 15 (officially an XM177E2).
Never had a malfunction with it. Of course I had learned, and paid attention to, the proper cleaning procedures.
No personal touches except for an AK 47 mag reworked to be a 35 rd M16 mag. This is what was carried in the weapon with 20 rd mags for reloads. Learned this from the Navy guys working "Market time" down in the Delta.
Nothing, I scrounged what ever I wanted to go with it. Used a 2 qt canteen strap as a top mounted sling.
I currently have an AR15A2, CAR 15 (built on an early SP 1 lower with parts I sent home from RVN) and an AR 15.
Here are some photos. The 3 M14s are all chicom - An M1A type and 2 M14 select fire rifles. At the top is an FN/FAL select fire rifle. The AR15A2 is not in the photo.
Sarge
Attachment 82507