The GP100 is bigger than the Kframe S&W's. It is more comparable in size with the L frames(681, 686 that you mentioned).....If the holster is codura, probably so. Leather, doubtful because of gun contours and such..........hpg
The Ruger GP-100 is larger and a much stronger handgun.
The 586/686 handgun is an "L" frame, not a "K" frame.
The "K" frame was designed to be a police officer's CARRY GUN not an every day shooter.