I just started playing with the 50 Blitzkings in mine.
Earlier I had taken 52 Berger Match Target hollow points up to 36.5 of Varget (Fed210 primers, 2.350" COL, Nosler brass) and these were over 3,600 fps.
So if I were you, I definitely wouldn't push up beyond 36.5 unless you are going very slowly with a chrono monitoring what's going on.
35-36, to maybe 36.5 on the high end with Varget and a 50.
Now with Reloader 15, I'm thinking 37.5 might be closer to my real max at probably 3900 or just over. With RL15 powder and the 50BK, I found goodness at around 36.4. I won't go any higher than 36.4 or 36.5 with RL15 either though until we get into hot/humid weather again. I don't need that extra 100-125fps that badly.