Many people have come to this forum asking the same question, and fixed their problem using the same advice. If your brass wont fit in the chamber at the base, the base needs more sizing. A lot of times it is simply a mismatched die and chamber. I have remedied this issue just by switching dies, not even going to a small base. My 20 practical sticks at the base if I don't SB FL 223 brass that has been shot in my 223s.