Firstly you need to get your slugs, then the manual from that manufacturer. They have tested many, many load variations and only include the ones that are safe and have performed well. My rule of thumb is slower burning powders tend to be better as the tend to fill the cases fuller. 25-06 IMR 4350 was ok 4320 was great. But bear in mind the perfect load can take a while to find depending on the bullet weight and rate of twist in your barrel. Sorry to add more questions than answers but my best source of information was reloading manuals from bullet manufacturers. Read them cover to cover!
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