Years ago they "freshed" the bore. A wood dowel was fitted with bits of a file and each groove covered, then a shim, such as a thin piece of paper, was put under the file and the process repeated. The grooves only had a slight amount removed. On the lands- not sure but you could probably dip the ball in pipe grinding ointment- etc and polish it up. I am just trying to introduce you to this process- others on this forum may have the details on how to do it or search the net. Worse case scenario- a thicker patch, etc. when all done.