Wow I was going over some of my old load workup data for a 243 AI and I had settled on 47.4 gr of H4831Sc OCW . I had done a ladder from 42gr to 48grs at 2 tenths of a grain increments.
I totally missed it when I choose the load.The node i used was 3100f/s at 47.2 to 47.6... at 47.4 i had a velocity drop of 70f/s... round 12 and round 13 are 8" apart.
Iam scratching my head
It shoots .5 to .75" groups at 300yrd.

I just finished working up 20 rounds at two diffrent weights where the velocity and the nodes were with in an inch using two diffrent seating depths. the veloity for these loads were almost the same and were within a inch of each other.

Have had something like that happen before.

You have met the land of diminishing returns.

Id be more inclined to scratch my head if I shot a 1/2 group at 300 yards..

Does the wind ever blow where you are, HV?

At our range that could easily explain an eight-inch movement of impact at 300 yards.