I took my new 686 to the range today to shake it out. I first tried a cylinder full of 38 sp then one of 357. Nothing blew up or bent. So far so good. However, after about 20 rounds the action became very stiff. At first I thought maybe dirty cylinders but brushing them made no difference. After it happend a couple more times I correlated it to revolver being warm from firing. If I let it cool off, everything was fine but once it warmed up it started hanging.

Once I got home I stripped it and checked the internal lockwork just to be sure there was nothing stuck in there. The ejector rod is not loose. The cylinder gap looks good. The only thing I can see that looks wrong is if I put some empties in the cylinder and dry fire, the gap between the cylinder and the recoil shield is barely enough to let the cases pass cold. On my other S&W revolvers there is some room there

Unless someone has a suggestion for something else to try it looks like I will have to call Smith and Wesson and arrange to return it for warranty work.