the reason it works is because field conditions always change. lots of powder change. for instance I have a load with varget for a 22-250 that has the same POI at 100 yards in a 4 grain window. another instance. I burned up all the n133 for my 17 fireball. I started a new lot that is brand new. load sped up by 100+ fps. same POI. if a load is that finaky you don't want it. I load up 7 or 8 cases with different powder charges up to what I am pretty sure is slightly beyond max. The load that is most forgiving up to and past max is the one that normally gets picked.