I also got a new 6 inch 686 a couple of weeks ago. I cant remove my barrel either with the supplied tool but will try an 8 mil allen key. I would recommend cleaning the barrel, mine was choked with crap and definitely improved accuracy wise after a proper cleaning. The gun, for me anyway, is very challenging but hugely enjoyable to shoot. I love it and much prefer it to very expensive target pistols.

My own sights required a considerable amount of time to zero, but the gun is capable of good accuracy, only being let down by me unfortunately!

Andy