gain bore for loooong barrels?
After about, say, 30", slowly open the lands up (maybe grooves too?) by increments of .0001/1". By 40" you have a .301/.309" caliber and less friction on the bullet (=less heat, less stress = better performance, less failure) in your 30-416 Imp.
The trick would be to find how much you could open up without getting gas cuts. Just enough to ease the pressure of the long drive.
Would it work?