That's the question.
The OP cites to no published source for the loads he is using. Had he consulted published data, he would have seen that everyone I could find reached maximum well before 1000 fps.
What we need to be doing on this forum is keying in on clues like that which suggest the poster is not following proper loading procedure and providing guidance back to published guidelines and proper procedure.
Had you not read into my posts you would see I never said bullseye will produce 1000fps. What I said was given my results it would take 7+grs to get to a 1000fps which BTW I already knew because I had consulted several reloading manuals as well as alliant's site. I used 1000fps to make a point. Based on 3 data points 971fps is realistic.