you can always have the barrel "relined" , but as of now , with a firearm that is no longer supported by the maker, and parts no longer made, only gotten through
"parting out" other guns or scrapping them, one has to do what they can to make their gun "useable" I would NOT hesitate to replace a "bad" barrel, and being there is NOT a change of the caliber , in the cylinder itself, go ahead shoot and use, tell the next guy , or save the repair /work order, with the guns , I would tell customers to put the paperwork in the box, save it......OR , you can simply stamp the NEW caliber on the barrel, ANY gunsmith or tool /die maker, maybe even a "machinist" could do this for you, NO BIG DEAL........
all that being said, pitting in the bore should not have that big if any "affect" to the guns accuracy, how does it shoot ????? I know of folks that continue to shoot their guns, use them and they have bulged barrels, pitting, etc, the muzzle crown itself is the important factor.........