welcome to S&W. glad you are here.

the S&W model 686 is one fine .357 magnum revolver. there was a recall on early models of this type.

The recall/modification was to replace the firing pin bushing in the frame and the firing pin in the hammer to address an issue with some hot ammunition having thin primers which would flow back into the firing pin hole upon firing, binding the cylinder and making the gun unable to operate. This affected the 586 (-0 and -1) and the 686 (-0 and -1) and their fixed-sight variants (581, 681). Later engineering changes for those models (586-2 and on, 686-2 and on, etc.) had the modifications incorporated into the design

Open the cylinder and on the frame cutout where the "mod 686" is stamped, look for the letter 'M" stamped there too, if it's missing the mod/fix hasn't been done.

if your model 686 experiences any cylinder binding, S&W will perform the modification at no charge. just contact them and explain your issue.

__________________
There's nowt so queer as folk