Many thanks for your comments on the various calibers and rifle types. I have been interested in getting a "classic" caliber (meaning old) for a while and am looking at the utility of either one of these in the CZ550. I think the long, skinny bullets available for the 0.264 make it ideal for anything in Arizona (including elk or bear). The 160 grain bullets (of "premium" construction) will likely shoot through just about any critters.
I have done serious ballistics and components research in these calibers. I do not have first-hand knowledge about the CZ550. I like my other CZ and find it very suitable for the inteded purpose.
I will likely get a 6.5x55mm for the ability to shoot light weight bullets at coyotes, too. Maybe make it a good cougar rifle, as well.
Thanks again for your input, all. Any other comments, please feel free to vent or opine (but no bloviating....).
Cheers,