It seems the most satisfied users are reloaders of .223/5.56. As far as the M1A group, I was taught never to reload brass that had been fired through one. And I'm as detailed as a Chinese mathematician wearing a tight pair of skivvies when it comes to reloading, so I never had an issue with trimming over and over again. I just accept it as a part of the process.

It seems that if the case wants to stretch, and we stop it with the mandrel, the stress will develop eventually in the shoulder anyway - forming a bulge or giving signs of overpressure.