Here's some of my data...All are 6 shot groups, I shoot 6 because I always seem to have 1 "flyer", most of the time its the first shot down the clean barrel. All these were taken the same day, 65° ambient, 100yds with a 8mph L to R wind. I have sheets with 50Gr NBT's as well but didn't see anything better or worse than what these show. I clean the gun between groups as well...
The difference of .5gr of powder between the 1st and 3rd pic is frightening, I believe the 22-250 is extremely finicky.
(from left to right)
55Gr NBT
33.5Gr Varget
55GR NBT
35Gr Varget
55Gr NBT
33Gr Varget (best results)
40Gr NBT
39Gr Varget (Max Load) Notice the wild "flyer" bottom right.