Take an old fashioned pencil, insert it into a groove about 1/8 inside the barrel, and then drag it out of the barrel. If you feel the pencil catch on something at the crown you have a burr that was created by a dull cutting tool when the barrel was crowned. In that case I wouldn't fire even one shot, I would send it back to the factory for a warranty repair.
Note, if you don't have any burr present your barrel is most likely just fine and what you are seeing is the effect of the viewing angle, lighting, and the ECM rifling used today. I have an ECM barrel in my 610-3, 620, and 625 and can state with certainty that ECM barrels shoot just fine with jacketed ammunition.
At one time I got curious about all the cloverleafs encountered with my 620 so I scoped it and put in 6 weeks practicing twice a week with it off a rest. The result of all this work was a 7/8 inch group at 50 yards and a conclusion I needed to start reloading. Because at 20 bucks a box those 24 boxes of American Eagle 130 grain FMJ cost me nearly as much as the 620 cost new.
