I have a 1917 when I bought it it shot fairly well, until I decided it needed a good cleaning. Afterwards the bore was shinney but rough and pitted badly. Now it wont group in a bucket, throwing shots all over the map.
It's in the back off my closet waiting to be rebarreled.
Light pitting maybe cured with lapping ,but if you cant get it all out it will foul and not shoot so well. Although if the edges of the rifling are good and no pits break through it may very well shoot cast lead bullets well. I have a muzzle loader like that. It shoots patched round balls very well even though the bore looks like the Arizona land scape.
Pat