With the sporter stocks 1 or 2 sizes larger are about all they can accommodate . Sporter rifles in standard calibers will normally have #3 contours and the magnums have #4s If it is a magnum
a #6 would be about the largest you could go A #5 would add barrel weight and still fit without
to much stock removal.
The standard barreled rifles can normally support a #5 contour.