Crainbird- thanks. Yeah, makes sense about all the variables. I thought I read somewhere about a way to determine minimum seating depth using the diam of the bullet vs. the length of the neck.

I found a really good article about coal on the berger bullets web sight that really made all this alot more clear. It appears I had it backwards about how coal effects pressures. One important fact I learned was that increasing coal apparently can reduce velocity in a specific powder charge. Based on that, I guess I should first establish an optimum coal and then work on powder charges. Which may then again change the optimum coal. A vicious circle!!! But thats the best thing about reloading. Tinker, tweek, test; repeat as necessary.

Thanks again for your input.