Full length sizer not sizing all brass the same
Finally started loading rifle (.308) rounds. I loaded 20 just to get my feet wet, used them in my LR308 and they all went bang.
Now I'm in the middle of loading (.308) for my bolt gun. Don't have any fire-formed to my bolt gun yet but for "practice's sake" I full length sized more cases (will neck size only later). I noticed that 1 out of 10 pieces of brass will not wind up with the shoulder bumped back as far as the others and won't chamber in my bolt gun when I chamber check them.
Brass are Winchester, once-fired in my LR308, press is Forster co-ax, die is Dillon. I have the Hornady Headspace gauge kit (and it confirms that the odd brass out are not getting bumped back as far as the others). I have been raising the shell holder into the die counting to 5, taking it out, turning it 180 deg., and put the brass in again for 5 counts.
What am I doing wrong?