Are you looking for 6mm Belted Express Ackley, 6mm Krag Improved Ackley,6mm Krag Short Ackley or the 6mm Magnum Ackley. I have a copy of the Handloader Manual of Cartridge Conversion that list these 6mm Ackley's and how to make each of these cases from other cases. Let me know and I will get you the info.
If it is a true 6mm Ackley Imp. chamber, all you need to do is shoot 6mm Remington cases in your gun and they will fire form to the improved chamber without any more work on your part other than, perhaps, trimming to length afterward.