Per Hammerheads point about the bullets tilting easily, I had that problem when I first got my Dillon Square Deal long ago. I noticed the bulge in the case that mirrors the location of the bullet base would often be visible only on one side of the case, indicating bullet tilt. So I chucked the powder drop and actuator tube into my lathe and ground a Lyman M die contour onto it to create a little step at the case mouth that the bullet sets squarely into. Bingo, no more one-sided case bulges. A few are not perfectly even all the way around due to case wall thickness unevenness, but all-in-all much more square than before. This affects both accuracy and leading, IME. If you want to make the switch, you can buy the Lyman multi-expander die which comes with M-profile expander inserts in all the common handgun calibers.
The only other thing is that if you are loading flat meplat bullets, in particular, is to keep and eye on how much fouling builds up in the seater die. If your bullets come in a randomly packed box and have normal cast bullet lube on them, it can pick it up off the bullet noses and cake to the point it is actually seating bullets deeper. A little mineral spirits on a Q-tip will generally remove it without having to remove or adjust the die.
