I'm not much of a believer in this bit about calibre A being more accurate than calibre B.
When Winchester brought out the .308 as a commercial cartridge, it soon gained a great reputation with the bench rest shooters. Thus, the gun writer types who had gone into being firearm "experts," because it paid more than writing about decorating houses, filled their glossy pages with tripe about the fantastic accuracy of the 308 Winchester.
Then, one of the major bench rest shooters of the day put them straight. He said the 308 had no more potential accuracy than a 30-06, or some other cartridges. He said the reason it was popular on the bench rest circuit for 30 calibre, was because it recoiled less than did the 30-06.
I think that much of the great accuracy we hear of for such cartridges as the 6.5 x (something or other) the 257 and the 25-06, is due to lighter recoil, as compared to other hunting calibres.
And recoil does affect accuracy, whether the big magnum guys like to admit it, or not.
Long ago, the British military were great experimenters. Among their many tests on small arms was one regarding the .303. They discoverd that a 10 1/2 pound Lee Enfield, when shot by an average shooter from the prone position, moved back one tenth of an inch, before the bullet got out the barrel!
So what would that do to some shooter trying for a one hole group? Even with a heavy, for sporting rifles and fairly light recoiling cartridge.