hillbillyjake,
You could do no better than a .458 Winchester Magnum.
All else pales in comparison.
Yes, JES does .458 WinMag rebores and re-chambering, did one for Sir Jerry on a stainless .375 H&H M70 Classic barrel.
That is about like a No. 5 sporter contour, perfect for a .458.
Shame on Sir Larry for the .458 Lott request when he could have had a .458 WinMag.
I had a Ruger M77 "Mk I" in 7mm RemMag and it had a very slender barrel.
They might have made a heavier barreled version too ?
Barrel diameter at 24" length on the Ruger factory 7mmRM barrel is the missing info here.