AR15 with only 75 rounds out (with correct break-in) and noticed a nick in the rifling. After looking a little longer it turns out to be a small bur right on the edge of the rifling. Its pretty easy to notice just glancing down the tube. I first noticed after I had cleaned it and later my grouping went from .25 to 1.0 or worse! I have never damage a rifle by cleaning but dont know what else could have caused this. Tried brushing it, but no luck. Off to the smith? Any suggestions?