This wasn't done because Remington had a wild hair. It was done because the guys at Remington found that they needed more than -.004 to have sufficient crush on factory cartridges. The reason for this might have been some variation in shoulder angle on a particular lot of factory ammo (Remember, all ammunition is made to be within certain tolerances. The distance to the juncture of neck and shoulder is not necessarily precise. It is the measurment to the datum line which is precise).
Ackley made mistakes too. Careful study of his drawings and dimensions will reveal this. GD
I found this while Googling this topic and may explain Remington's reason for altering the original Ackley:
"Although Norma brass cases are more expensive than domestic cases, the outstanding dimensional consistency of the Norma 280 cases are in my opinion worth the extra cost. I have found that Remington cases are as much as 0.007 undersize and some with more than maximum headspace. Since all cases have to be fire formed the headspace is easily eliminated. But the bulge on the bottom can not, and will eventual allow for primer pocket expansion. These cases were made for semi auto rifles and intended to fall into the chamber."
