Higher velocities is the primary purpose for making an Ackley Improved cartridge. It is not difficult to make the improved cases. Today, because Nosler markets brass, it isn't even necessary to fireform, provided your chamber is cut to SAAMI specs.
the sharper shoulder and less body taper of the AI line allows it to make a lil better use of top level loads and makes case trimming almost non-existant.
hard to make, nope you just load up the parent cartridge or buy parent cartridge factory loads and shoot'em, then just load them up full power.
RR