The .22-250 Ackley (usually called the .22-250 Ackley Improved) is like all the other "Ackley Improved" cartridges in having a slightly blown out case and a sharper shoulder than the (now) factory .22-250. The factory .22-250 Remington is itself slightly modified from the original .22-250 Varminter.
The only way to get a rifle in .22-250 Ackley Improved would be to build one or to buy a regular .22-250 and have it re-chambered to the improved case dimensions. Either way would mean paying Clymer or someone to make a special reamer, as the AI cartridges never were standardized and (AFAIK) no reamer company has them in the regular line. In addition, as Harry points out, it would be a handloading proposition for which special dies would also have to be made. All in all, it probably would not be worth it unless you just want to "pay to play" and try for all you can get out of that old cartridge.
When we read today about all the things the old timers did, we forget that they were all highly capable machinists. Making reamers, making loading dies, even drilling and rifling barrels were no big deal to them. Many (most?) of today's gunsmiths (and I say this with a degree of sadness) can barely install a pre-threaded barrel.
Jim
