"I'm not sure if Lowegan is saying that he recommends a larger forcing cone or that Ruger is using a larger forcing cone. People commenting on that thread are saying that they have newer 7 shot GP's and are not having any issues. Still, I'm glad that I have the 6 shot. Thanks again for the link"
I think he is saying that Ruger is using the larger forcing cone. The overall angle of the tilt of the chambers must be very small, thus, the lack of reported problems with the "fix". With respect to the 686 I don't know if S&W actually changed the frame between the 6 and 7 shot models or just got lucky in having the 6 shot ones originally engineered with a slightly larger diameter cylinder than the GP100. On the N frames when they went to an 8 shot model they did increase the space between the cylinder axis and bore center. So, it must not have been too costly to modify the frames for the 8 shot models.