I will give it a try.
Sometime in the past there was a gent named P.O. Ackley who was involved in wildcatting existing cartridges. His modus operandi was generally reaming out the chamber of many different cartridges to lengthen, remove some taper, and make a sharper shoulder, Usually 40 degrees instead of the standard 23 or whatever.
He made claims of 2 to 3 hundred fps improvement over the parent cartridge. Usually it was more like 50 to 100 fps improvement.
Normally the parent cartridge could still be fired in the improved chamber which in turn "fire formed" the brass to the new dimensions.
Most reloading die makers carry Ackley improved dies with varying shoulder angles. They are usually more expensive than standard dies.
There are also claims that Ackley improved cartridges are generally more accurate than the parent cartridge, but I cannot verify this claim.
I have been interested in the Ackley improved versions of several calibers, but never enough so to have any of my firearms "Improved"
Hope that sheds some light on the subject but I may have left out some important details, as I don't claim to be well versed on the subject.
Dave
