anybody know what type of ammo was used.  Gr. size , brass case, steel case?

Most of the ammunition used by the Communists in Vietnam was supplied by the Chinese. It was  copper washed steel cases. I can't tell what the bullet weight was. They were moving too fast and I was trying to avoid catching one. From later purchases, I believe that the bullets were steel core, but that is far from certain since I never disassembled one when I was there.

I have a box of "sterlized" American 7.62x39 which uses a brass case and a 123grn FMJBT projectile. It looks very similar to current Winchester white box 7.62x39, except that there are no markings anywhere on the round. They came in a plain white box with black letters that say "7.62x39" and undernieth that it reads XXX-XXXXX-58-71. I have been told it was manufactured in 1971 at the Lake City plant as they made the majority of sterlized 7.62M43.
During the cold war, obtaining 7.62x39 wasn't particularly easy so we were forced to make our own to supplement our captured stocks. There was a process for capturing weapons/ammo and they were catalouged and actually used for combat/training. Chuck used primarily Chinese ammo, but they also used Russian and other communist manufactued ammuntition. Not sure if this answers your question or not, but "sterlized" 7.62x39 looks very similar to current production WWB.

cool!!