Hello everyone this is my first post on this, hopefully someone will be able to help me. I have the 20 inch 8 shot persuader 500, and I'm wonderin what the hell makes a 590A be able to have that one extra shell. do they count the speed loader stock or is it actually a extra shell in the magazine tube? I've heard many people say it's the mag tube, If it is in the tube how can I make mine have the one extra?