You Ackely ballistics are almost as inventive as old P.O. himself!
A contemporary quote:"The typical Ackley Improved case gives a modest increase in velocity over the parent case - as long as both are loaded to the same pressures. All one has to do is look at modern tested loading data to verify this - the latest Nosler manual has a number of Ackley cartridges, and the average increase in velocity is on the order of 100 fps. This is simple ballistic fact, not clouded by the rantings and hype of guys trying to sell a product. There is just not enough increase in the case capacity to make a big difference in velocity."
