I think my having the horizontal vs. vertical issues was I was right on the edge of not enough powder to blow out the case. I already had a batch loaded up and the vertical shot cured the problem.
Continued doing on every subsequent fire forming I've done.
Worked for me and in these days, less powder is always a good thing.
The idea of the 270 then getting a full profile of chamber is a great idea. I've never heard it before, just hope I can remember it the next time I need to figure out a chamber. Probably not, but I can hope.