I just re-read this thread to make sure I wasn't duplicating someone else reply. I have an idea: how is the muzzle crown? This is sorta a trick question, because often an imperfect crown is not readily naked-eye visible. What I did a couple of times back in the dark ages was use a fine abrasive rotary stone, spherical or conical, doesn't seem to matter, and twirl it in the muzzle lightly while watching TV. You can feel it smooth out. Problem is, its a new gun, and what I'm suggesting might blow the warranty. I don't know any way that you could prove to the manufacturer that this was the problem.
OldBob