Back in the 60s the my neighbor fixed barrels that had a lot of pitting ... What he would do is he had a big handle off a old push lawnmower with a long steel rod and a washer  that was rounded off so 30 cal.   He would put the rod in the barrel and pore in bullet lead and use valve grinding lapping compound and run the plug up and down the bore and restore the bore and rifleings ... Back then a lot of people used cast bullets so if the bore was over sized it didn't matter ...