My guess would be a PPC gun: PPC (Practical Police Course) was one of the first "combat" style competitions. It was hampered by (a) entry restricted to working POs, and (b) no limitations on revolver modifications. Add the fact that you could shoot with whimpy loads, and you got a revolver with essentially zero recoil that held target without any movement.
However, that appears to be a Dan Wesson and I never saw a Dan Wesson in a PPC match. Most were built from S&W M14s, with bull barrels, full length sight fixtures (often filled with melted lead for more weight), beveled charge holes (to aid speed loader reloading), and adjustable rear sights.