That area is known as the forcing cone. It is the area that reduces the chamber size down to the bore size. It is cut thru the metal on a bias compared to the parallel section of the bore. A difference in appearance in this area is not unusual but it can be polished and often a pattern improvement will result from polishing it. The rings you describe are called tool marks. Some barrels are better machined than others. If you want to do more than a polishing will do, it requires a hone and I recommended that you have a gunsmith do that. They can also lengthen this section which makes for a easier transition for the shot into the bore. This can often improve patterns with lead shot but tends to not have a lot of effect on HTL shot.
