I also do not do anything to the case mouth. My Winchester and Rem-UMC hulls, which are about the same thickness as Magtechs, are probably over 50 years old and loaded unknown amount of times (about 50 by me) with no splits. However, I will admit that a slight roll on the mouth might make them a tad easier to chamber into the shotgun. And I would assume that annealing would help prevent splits in that case.