Parker Ackley never did a .260 AI, so finding the exact loading will not be easy. I'd just start with a good stiff load for the .260, and sorta "creep" my way till the case expands about .0005" near the base. Then back off about a grain of powder. Be very carefull when loading those long bullets in that short neck as the bullets often end up deep inside the case. If so you need to back the charge off about 10% and work your way thru it
gary
