All the full distance matches I've shot were 600, so I've never shot at 500. Most of my matches were at ranges limited to 300, so we shot the reduced target for prone slow, the MR-63 target.
I did hear that some ranges went to 500 for the prone slow, but that was not what they were when I shot matches at those ranges. My first points towards Distinguished were at Camp Smith in NY, and their 600 yard line was on a hill overlooking the range complex. They don't use that line anymore since it required so much of the complex to be shut down by fire control during that phase of the matches, they go with 500 from the base of that hill. (or so I've heard)
Still some nice shooting with a wood-and-steel rifle that has some recoil.
