Jackie, I'll lean ya toward a .270 Win.; 257 Roberts, or AI version; 7x57, or, AI version. Per Al Nyhus (post #14), I chambered a pair of 35 Whelen barrels for my Pal, Tom, which have exceeded our expectations. The better of the pair, on an older & trued 700 Rem., featuring a Wilson #4 contour barrel is a real 1/2 MOA rifle!
We had it out to THE RANCH last fall and Tom collected dope from a 200 Yd. zero, out to 500Yd., @ 50 Yd. increments (used IBS 600 Yd targets) - it delivered 1/2 MOA (4-shot groups) all the way. We were both surprised. That said, Tom will likely never even shoot over about 300. It was an interesting and fun project.
Still, I'm going to re-barrel my old Mauser (my first center-fire rifle, which my Dad gave me just prior to my 16th birthday), to 7x57 Ackley Imp. That rifle was a model "1935 Peruvian Mauser, Fabric National" - I believe in Belgium - and was originally a 30/06. At age 26, I had it barreled by Shilen, with a Hunter taper "select match" in .270 Win. That rifle, has always been a "shooter" - collected a lot of coyotes and mule deer, but finally, burned it out. The "classic" cartridges are just THAT - great performers all. RG