Tom,
I had a high school buddy who ended up in country the same time as me. He was with a Combat Engineer unit down south of us, can't remember exactly which one it was, but we used to exchange in country letters. Anyway, his unit had to go out every day from their base camp and repair the roads and bridges that the VC/NVA blew up. He happened to be on one of the gun trucks providing security one day, it had a quad 50, and his guys were repairing a bridge, when a VC jumped out of the bushes along the road yelling "Chu Hoi". My buddy yelled back "Chu Hoi this M---er F---er and opened up with the quad 50.
Nuff said.
George