you should be able to load near max regular .243 loads to form the improved case. the hodgdon annual manual(around $7) should list 15" .243 data.
i am forming 30-30AI with max regular 30-30 loads, and it works great. then work up slowly after the cases are formed.
you can also shoot factory .243 loads in it to form the case. this also works fine in my 30-30AI. you may already know this stuff, but just trying to help.
