I think at least based on the experience so far with my 264 WM, it looks like total powder burned is the first factor, then the second is burn rate of the powder, or time for the heat to conduct into the barrel. These are probably not unique, and they are intuitive, but I was thinking that maybe peak temp of a fast burning powder was more of a factor than it appears to be. Total heat and time for conduction appear to be the drivers that I see.
There is a significant difference in heat between Ramshot and RL33, but RL33 is still slower, and I'm wondering if at lower pressure the RL33 consists that much slower than Ramshot. I'd still like to try Retumbo but can't find any around here for sale or through Midway.
