Jeffe,
Have a quick question about rim thickness vs "generously" cut head space.

I measured the rims on the Norma 45/120 brass and it is .069-.070, All my starline 45/70 brass is .70 and the headspace on the Buff classic measures .0725. The rifles I have set headspace on have been bolts 338 fed, 338 win mag, 30/06 and the headspace on the mag belt has to be more generous. I was told to measure the thickest rim I was planning on using and headspace a thousandth over that. Would it be to much to go to have .0025-.0035? and would that cause primers to set back as you mentioned?

If so I can wait till I build the double and get it right.

Have a good evening