If one increases the case capacity by 10% in a given bore size, say 257 Roberts to 257 Roberts AI for example, what is the rule of thumb for the increase in powder charge? I suspect that making the case 10% bigger does not just let you use 10% more 4350.
I know Mr. Barsness has a rule of thumb for increasing case capacity relative to velocity gain of 4 to 1, so I recognize that velocity gains for the 10% case size increase should be on the order of 2.5%.
Just wondering if there is a guideline that lets me predict appropriate powder charges if the increase in case capacity is known.
Thank you.
Last edited by tcp; 04/21/15. Reason: bad math
