A far easier method to work up a load is to use a ladder method, whereby you increase powder charges slowly, shooting at the same target, and noting thier impact point.
Then you find the charges that group closest together, and make samples of those to shoot into groups. Shooting one target of 5 rounds of .5 gr difference is a waste of time and bullets, as you really onl get to know what that particualr group did, and you may have pulled a sht, the wind picked up or the hand of god intervened to make a one hole group, never to be repeated...
I found that in my Stevens 223, a 55gr Ballistic Tip wiht a max load of Benchmark (25.6gr IIRC) and a Federal primer worked very well. Work up...