Here is how I go about making whisper brass from 5.56 NATO.
First the pic:
Far left is the virgin 5.56 NATO
1st Step: Use small pipe cutter to cut the case neck off just below the should.
2nd Step: Lube the case up with STP oil treatment, ram it through the redding size die with the .30cal button installed.
3rd Step: Trim to final length, my gun does best with a trim length of 1.350", normal trim length is 1.335"