Jimmy, It didn't bother the finish on the gun I used it on. It had an oil finish, your results may vary depending on the type and condition of finish. I use a fine mill file for most of the final cut down and fine sandpaper just to clean up the file marks. It helps if you glue the sandpaper to a block and be careful. The rough work is done with the plate off of the stock.

Jim

I learn something every day, and a lot of times it's that what I learned the day before was wrong