I enquired on relining my Lee Speed before re-chambering to 338/303 Nitro Express and no relining outfit or gunsmith would take the job for this very reason . It would have to be custom because relining companies stick to lower pressure jobs. The JES re-chambering was quite simple :the bore was just drilled out to 338 ,the 303 head-space stayed exactly the same with the 338/303 just a different bullet . The same thing as taking a 25-06 and re-boring it to a 30-06 ....Interestingly after re-boring I fired a box of 303 British Winchester hunting ammo out of the rifle to obtain the brass with no ill affects ( remember the headspace is exactly the same ) The groups with the 303 Ammo still hit into a 6-8" group at 100 yards with some keyholes but was no worse than the original shot out 303 bore . My 338/303 reloads in the new bore shoot cloverleafs now at 100 ; quite an improvement over the original !