I lurk here frequently but only post when I'm buying stuff in the "for sale" section. I hope this is in the right section, I apologize if it isn't.
How do you determine a safe starting load for a powder and cartridge combo for which there is no load data?
Case in point - Longshot in 44 Russian under a 180gr LSWC. There's no data for Longshot in a 44 Russian.
How would you determine a starting point for this load?
BTW, I'm shooting this in a S&W M629, so going slightly overpressure is not a concern.