358WCF,
Pushing Ackley Improved cartridges "hard" is the primary reason they supposedly get significantly more velocity--and always has been. Only a few Ackley Improved rounds get 100 fps more muzzle velocity when loaded to the same pressure--and those are older cartridges with far more body taper than the .338-06, such as the .250 Savage. In most cartridges you can get within 50 fps of the same muzzle velocity by pushing them hard.
I have fooled with a bunch of Ackley (and other "improved") rounds, and so far the only significant difference I've found is the near elimination of case-stretch--which saves a lot of time in reloading hundreds of varmint rounds, but not much in big game cartridges. That said, a lot of recent varmint rounds have a sharp enough shoulder to result in essentially the same thing.
But whatever.....
Do you find , while case trimming is much reduced, that the neck / shoulder junction will thicken over many cycles?
This is what I have found with a 6 Dasher and 280 ai. This makes closing the bolt a bit harder than normal , so neck turn the base of the neck.
Improving a cartridge is not about velocity (for me), but getting it 'right sized' to give more opportunity to hit an OBT at reasonable pressures.
