Thanks Larry. Now that I think about it, I have seen similar marks in the barrels of a couple of my older .22 rifles, but those marks didn't appear to be as deep as those in the S&W.
Beemer-mark, the gun appears to be very accurate, except for the odd flyer, which I put down to defective ammunition, shaky hands, and/or failing eyesight. Shooting two-handed, with the butt resting on the shooting bench, its pretty much a tack-driver at 10 yds.
Islandguy