I'll double up on what Jimro said. I'll just add that your weight increments are about twice what Dan Newberry's OCW method
employs, for the reason that you can miss a sweet spot or at least fail to find its true center with bigger increments. He uses 0.7% to 1% times the load as an increment, so, within practical limits, either 0.2 grain steps to 0.3 grain steps in your case.
If you use 0.3 grain steps, I would go from 23.9 to 24.5 grains to start. If all three did not look good, I would switch to 0.2 grain increments and go from 23.8 to 24.8 just to see if the center of the accuracy range gets easier to identify.