Otto,
I would think your speculation about the source of the excess headspace is as good as anyone elses.Since you have another 8.15x45R project(and I'm selfishly glad to locate a reamer)I won't recommend taking excess headspace out of the cases by fireforming and setting the sizing die to just "kiss" the shoulder, nor by moving the case rims forward like we did with the 45-70 to make Mauser "A"base cases.I don't know if .012 is too much, but you do need some space between the breechblock and barrel, otherwise you may have trouble with seating some cases.You want the breechblock to bear against the casehead rather than the barrel(I didn't think this up out of the blue, I made a similar mistake before).I too am having fun with this project, and I didn't have to pay anything.
Mike
