Two things to consider: 1. Errors in shooting/hitting do not add linearly. It's more of a square root of the sum of squares result. Because of this, halving a small error can well produce less overall improvement than a 20% reduction in a larger error in the combination. 2. It's quite feasible to shoot below MOA out to 300 yards with thrown charges of even long stick powders like 3031 and 4064. I do it all the time with sporter weight rifles. Other ducks, like the straightness of assembled cartridges, need to be in a row before (assuming a well developed load) small variations of charge weights amount to much.
