By design The lee collet dies have a floating collet, it is because of the flaoting part that alows the brass to munipiulate itself, or the die, insted of the other way around. (Meaning a traditional die is solid, and the brass must conform to it.) Now, because of the floating collet, if the brass is harder on one side, or thicker, it will push the collet to the other side. (From my experience it cause concentricity problems as well because of this.) Now on the donut forming I will take a quote directly from Lee's web site about the die. "A collet squeezes the case neck against a precision mandrel for a perfect fit with minimum run-out." Notice the word "squeeze." As it is doing this it is pushing the brass back against the shoulder making the donut you are seeing. It has been my experience that this dies causes donut problems. Lets put it this way, if this was truly a better mouse trap you would see other die companies designing similar design dies. If it truly was as Lee quated "Smallest group size or your money back." (Lee not woried about giving someone ther $38 bucks back.) you would see people using them in benchrest, I have shot matches all around the country, and I can say I have ever seen one person use a lee colllet die, there is a reason. The people who swear by them just dont know any better.