What I like to do is start with 20 rounds of each bullet powder combination. Loading 4 rounds of equally spaced powder levels between the manual's minimum and maximums. Then I shoot a 3 shot group of each load, with a spare round in case I call a flyer. Comparing the groups I chose the best and start to vary the bullet seating depth to see if I can improve the accuracy. A word of warning here, do not load bullets so shallow that they touch the lands in the barrel, that can change the pressure enough to cause trouble.