I had a 1-A 257 Roberts, had the same bumps on the lands, visible at the crown. The bumps were visible because they used to foul really bad. Friggin gun wouldnt group for crap. Sent it back to Ruger on their dime, it came back as tested OK with a test target and nothing done. Called about it and they said the accuracy was within their tolerance. Test target showed a 2" group, so I asked them what ammo they used. They were using a Federal load that isnt made anymore, at least I couldnt find it. Then they told me that the group was shot at 50 yards. CS person refused to pay for the gun to go back.
Sent an email to the CEO, got a call to ship the rifle back. Came back about 2 months later with a not stating that the barrel had been replaced. It still had the same bumps in the same spots. Gun went down the road.