I've chronoed a bunch of h13 6s at 950-1050. Shot one at 50yds once that only chronoed 975 and it blew threw sheet tin. Shoot a CP lead #6 at 1300 and the pellets bounced off the tin.
Don't worry about the MV you have now, find the distance it falls to 100, call it your max under calm/warm conditions, and go pile up some toms.
Good Luck
Reloader