An excellent shot, indeed, congratulations!
Most folks don't realize a good revolver and load coupled with sufficient practice are fully capable of such long shots. I won a "long range" revolver side match a few years ago by putting 5 for 5 on a 12" square plate at 85 yards in under ten seconds with an 8 3/8" Interarms Virginian Dragoon .44 mag and reduced loads - stock iron sights, no scope.
I took this little 3x3 mulie a couple hundred yards from my house in 2006 with a Freedom Arms M555 .50AE topped with a 2x Leupold scope at a lased 145 yards.
The rest of the story is he was grazing directly away from me, so I laid down prone with the FA across a stump, and whistled. He didn't turn but looked over his shoulder toward me giving me nothing but a head shot. I had shot this revolver quite a bit out to 150 yards and felt confident I could do it. I squeezed the shot off and put a 350 grain cast WFNGC bullet up the right nostril.
I killed a cow elk the same season with a S&W .500 mag topped with a 4x Leupold and using the same bullet at about the same range as the OP - body shot though, not a head shot.