When I first saw the crack I thought there had been a bulge at that point in the barrel, but there is no sign that a bulge was ever present. No ring is observed when looking through the bore. There is a dent that has been mostly pushed back out with the crack running through it. When I get time I will measure the wall thickness at and around the damaged area. If the wall thickness is thinner near the crack then a repair will not be attempted. Thanks for the replies.