The second time it shows Robinson target shooting in the desert, he is shown loading his gun. When the cylinder is closed there is one empty chamber, meaning that he only has four shots loaded in this five shot gun. When he starts shooting at the target, however, he shoots five times.
Robinson is following Dolan's Cadillac to Los Angeles and at the detour, the sign points "DETOUR" to the right yet the highway flag-person sends them to the left into the desert.
When Robinson target practices with his pistol, the camera gives a "down the barrel" view. The interior of the barrel is smooth. All pistols have a rifled barrel (as shown in the famous James Bond film introductions).
The highway where "Dolan" is "buried", according to the film (shown on a sign and on the work order) is US Highway 71.
US 71 is nowhere near Las Vegas or Los Angeles. It runs from Southern La. to Northern Mn.