I've been shooting more fallow of late and and contemplating something with a bit more punch than the 243 - mine loves 90gn bullets, so it's probably a bit on the small side for a large fallow buck - perfectly capably when I put the bullet in the right place I know, but nice to have a bit in reserve if the shot isn't quite perfect! I reload, so don't mind something that is not readily available, in fact I really fancy something a bit different.
Trouble is, I don't know what!! 6.5x47, 260 etc are all just a bit similar ballistically to the 243 to really make it worthwhile running a second calibre. I'm not going to be firing thousands of rounds, so something a bit "hot" doesn't worry me and if I want something that shoots a bigger bullet as flat as my 243 then it's going to need to be quick...