I don't have access to my loading notes, but I have got the Hornady 125gr HP bullets up to about 3000fps with them still hanging together. However, I have an extremely smooth barrel (made by Border, if anyone cares) which I think helps a lot.
John, I might try the Hornady, I think mine were some bulk remington 125s and I could get a chrono reading at higher speeds but could not find hits on paper. Had to move the paper to 25 yards and the sharpnel was leaving a 4-10" pattern. They do fly like marshmellows though, I keep them inside 100 and things are fine.