I am very new to longrange shooting but sent my Zeiss Conquest out to have target turrets put on it. Now I am wanting to order Kenton Turrets. I do my own reloading so was looking at there TTC#2 order form. Problem is I do not know the answers to most of the questions on the order from. I know I can get the velocity from a chrono. Where do I get bullet b.c from? What about barometric pressure? Sorry if this seems like an answer I should easily know.