Your rifle sure likes that bullet and powder. I am surprised to see the big drop in elevation on the 8th shot.

ADI 2209 - ie: H4350 seems a good powder for this ctg., however, few handloading books here list it.

Interesting method. Reminds me of Barnes suggestions.

Pick 3 or 4 different powders that are suitable.

Load one round of each from start load to maximum, 1/2 gr. or so between loads.

Fire them into groups - one powder per group. Pick the powder that gives the smallest group, then work with that powder as it is the most suitable for your rifle over a variety of speeds that temperature swings used to give us, easily 150fps load to high.

The newer temperature stabilized powders somewhat reduce the variety were were so plagued with in years gone by.

Nice to find a good shooting load in the higher end of the load developement.