Coldmaker's right, the pic shows an Audette Ladder test. Newberry's OCW is on the same basic principal but involves shooting "groups" of each charge weight onto separate targets and looking for a common impact point.

Now for my recommendations, I really can't tell anything by looking at that pic. In my opinion, ladder and OCW tests need to be conducted at ranges of no less than 200yds, and the farther the better if both the rifle and shooter are up to it. At shorter ranges there's just so much overlap in impact points it's had to decifer much of anything, which is exactly the problem I ran into when I looked at the picture. If by some chance that target happens to have been shot at 200yds or more, then the rifle is certainly accurate, you just need to go farther out before you can diagnose which load is best.

As for temp stable powders, very few ball powders are temp stable. They flow well in powder measures, but temp stability is a typical problem. Ramshot's ball powders could be considered one exception to this generality. Extruded (stick) powders are generally more temp stable even though some of them aren't very good either. Personally, I like Hodgdon's Extreme series any time they're applicable, but Alliant's ReLoder series isn't bad either.