A friend bought a 1903 Springfield from the CMP that had a sewer pipe bore. It would fray cloth cleaing patches when he tried to clean it. No accuracy and some bullets would key hole at 50 yards. After going through the fire lapping procedures using all three grits, he could keep a 4-5 inch groups at 100yards and some shine returned to the bore.
Not a tack driver, but did turn it back into a plinker at least.