I had to run all my 20P brass in my RCBS SB die since the brass I sized down would not chamber.
Its an added step overall IMO. I had no problems chambering after that, but did on extracting after being fired on a handful of brass.
I was using LC/r-p/win brass, so brand wise it didn't matter, still had to run them in the SB die.
Make sure your brass is trimmed to 1.750" also. Anything that was 1.760+ failed to chamber also due to length.