RE: Wanting to complete my rifle battery have ?
I have a .264 Win. Mag. and a .35 whelen to fill the two niches you describe. The .264 isn' t really a whole lot hotter than the .270. The .35 whelen isn' t too far behind the 338 mag.
I like odd cartridges and find I usually fall in love with a particular rifle and then buy it weather or not it is the logical choice.
Robin