Re: caliber chiose. 260 or 7mm-08
First, I haven't tried changing brass casings from one caliber to another.
But, from what I have read, the theory of using several dies to go from one casing size to another is that you choose one or more intermediate sizes so that you only stress the brass a little at a time. In so doing, you are much more likely to obtain the desired results than if you try to do it all at once. If you try too much at once, you run the risk of the metal moving unevenly, and thus creating dimples or rings. The rings would indicate that the shoulder was being pushed to far too fast, and the lower case was not strong enough to handle the pressure, so it wrinkled, forming a ring. This could also explain the dimples in the other, as the case held up, but the shoulder metal wouldn't flow properly, so it dimpled.
Another possible reason could be that the brass you tried to form was not the proper hardness for what you were doing, (my guess is too soft), so it buckled in areas that you didn't want it to.
Again, I don't have practical experience here, so what I am saying is book knowledge.
I would appreciate if those who do have experience could weigh in to help me know if I am learning correctly here.