There is a factory memo in one of Speed’s books that gives factory mag box length and width dimensions. I don’t recall if it gives depth. I can try to dig it out later tonight, or perhaps someone can beat me to it. However, I’ve notices that rounds with wider shoulders and bases have the inside of their mag box walls scalloped. That is the case with my Oberndorf 9.3x62, anyway. It’s a standard depth mag and holds 5 down.