How do I get scratches out of a Woodsrunner barrel before bluing it?
Start with draw filing, using a single cut mill file held roughly at 90 degrees to the barrel's axis and pushed along its length rather than drawn toward you, which gives a good finish on its own. For a finer finish, follow up with abrasive paper starting around 150 grit and working up to about 320 grit depending on how fine a finish you want.