Re: 270 wby brass
there's .006" difference in the length, and that's not anything to worry about. Looking at the case drawings in the AA manual, it looks like all you have to do is neck the 7mm brass down while keeping the same headspace (they are within a thousandth or so). Then simply fir form the 270 mag brass. It'll probably shrink about .010" or maybe even less on the overall length. They even have nearly the same radi in the shoulder (within .001"), as well as the same shoulder diameter.