I have owned and loaded for both,but never got to kill anything the few times I hunted with them.I liked them both but to be honest I could never see that either one did anything that couldn't be accomplished nicely with a garden variety 7mm Rem Mag.(which sort of makes sense because the 7RM buried both of them pretty much).
So, I sold them.
Both these cartridges were introduced before a common 7mm magnum was commercially available.
If choosing I would get a 264 simply because it comes in pre 64 M70's...although that Weatherby custom on the Mauser action posted above is pretty funky and cool.
My 270 Weatherby was pretty sweet....pre 64 action, Lilja barrel and Bansner stock...the guy who bought it from me said he might want to sell it back to me....but I dunno if I want it....I got a 7 Mashburn.It's better than all of them...
