Although my gunshop is only about 90 miles from Trinidad, Colorado - where P.O. Ackley taught gunsmithing - it is amazing how many gunsmiths in this area don't understand how to set up an Ackley Improved chamber. The bolt must not be able to close on a "go" headspace guage, but should be able to close (with a little umph) on a factory round or a virgin brass case. Before fire forming, the case is only touching the chamber at the juncture of the neck and shoulder. The overall length will shrink when fire forming, and after that there is almost no need for case trimming.

They will typically produce 150 to 200 fps more speed than the parent caliber, and often will need a little slower powder to do so. RL22 has really made the family of Ackley Improved calibers based on the 30/06 come alive. It burns a little slower than H4831, but takes up less space in the case. The .25-06, .270, and .280 Ackley Improved's are all at their best with RL22.

One of the best Ackley Improved's is the .22-250. I have mine "loaded down" to 3800 fps, where I have reloaded a lot of Remington brass over 20 times. Without ever trimming a case. It shoots 1/4"