I would think IMR 7828 or H1000 would be excellent choices of your choices I would try reloader 22. There is very little data out there as the space in the case is displaced by the bullet to much.
The 140 NPT data for reloader 19 starts at 41 with a max of 45 its construction is not totally different from the mega lapua a little shorter. Starting at 40 would seem appropriate. Watch out in higher temps with RL19 I had a bad experience with it one summer with a full charge in my 30-06.
Good luck and shoot straight.
Bob
