We've discussed this in the past, but I screenshot some better images

[Linked Image from photos.smugmug.com]

The pheasant hunting scene starts about 1:16:45. I couldn't find when pheasants were introduced to Colorado, but they were not brought to S. Dakota until 1898.



The movie is set in the 1890s in the 4 Corners, near Mesa Verde, which is in Colorado, but the courthouse scene has an Arizona flag flying - which did not exist until 1917; 5 years after AZ became a state.
The film was shot at Old Tucson Studios, west of Tucson, and the San Rafael Ranch House is now a State Park near Patagonia.
The end of the Comanche Wars was in June 1875 when Quanah Parker surrendered at Fort Sill. The Comanche were not in NE AZ nor SE Utah.
This site claims the double was a Parker, which it clearly is not
http://www.imfdb.org/wiki/McLintock!

[Linked Image from photos.smugmug.com]

Watch carefully and G.W. appears to load the gun with what look to be green plastic shells.
The White Line pad does not appear to be perforated.