Way back during the last Ice Age ('60s and '70s) I did quite a bit of reloading, shooting and hunting with the 7mmRM and 264 WM. Never could see that first whit of differnce, even with the 175gr loads in the 7, and eventually kept the 264 and sent the 7 on its way.
As a sidenote here, I had several boxes of 7mmRM 150gr Remington factory loads that generally gave sticky bolt lift - turns out that lot had been recalled, but at the time I was living out in the sticks and wound up shooting all of them.
I purchased a Mark V in 270 WM with a 3.5x10 Leupy in perhaps 1975 and still have it. I cannot honestly state the round is any better killer than a 264 or 7RM, but this rifle/scope combination has proven to be the most consistently accurate one I have ever owned. I lugged it up into the Alaska Range on two sheep hunts, took about every species of Alaskan game with it (no brown growler or goat) and have taken it Africa twice (Zimbabwe and Namibia both times). I suppose having confidence in it counts, but I cannot imagine anything in this power class being better.
I've never owned a 257 WM or 240 WM - yet....
