RE: vapor trails
I saw that effect once with a .223 while spotting for a friend. A similar incident occured during a rainstorm. I was just about to pack up and go home, but I figured I'd put another magainze through his HK SL8-1. Apparently the first shot put the bullet through a couple of raindrops because I could hear the sizzle up close and see a tiny wisp of steam further down the range.