My understanding:
30-221, 300Whisper, and 300BLK are an evolutionary set.
Each step is changed enough for patent purposes, (get or avoid), and yet similar enough to be interchangeable. The last 2 have an owner/sponsor that advises against using the other 2 "for safety reasons". Since the differences are in the shoulders and the shoulders are tiny, Handloaders can swap brass and load data between the 3.
Right?