John Sturges had an alcohol abuse issue during filming and was supposedly often drunk on set, resulting in the assistant director taking over the camera on more than one occasion. Apparently Clint Eastwood was annoyed and disappointed with Sturges' lack of professionalism during the shoot and felt it compromised what could have been a great movie. These thoughts would be echoed by Michael Caine three years later during production of L'aigle s'est envolé (1976), where Caine felt the final film did not reflect the quality of Sturges earlier work due to him being constantly distracted.
Writer Elmore Leonard certainly did know something about classic firearms. From Frank Harlan's (Robert Duvall's) Custom Savage 99 (1899), Olin Mingo's (James Wainwright's) Remington-Keene sporter (1880) in .45-70, Lamarr Simms' (Don Stroud's) Mauser C-96 (1896) broom-handle, and Joe Kidd's (Clint Eastwood's)) Cased Ross Rifle sporter model M-10 (1910) in .280 Ross. Leonard took special care to ensure all weapons (even the optics) were period accurate for that movie, being set in pre-statehood New Mexico territory (1912).
This is the last time someone else (John Sturges) directed Clint Eastwood in a western. Eastwood appeared in four more westerns, all directed by himself.
In an interview given to French student Emmanuelle Laborit in 1990, John Sturges said he had a lot of problems directing Clint Eastwood, and regretted that he did not resign during filming.
The impressive outdoor scenery is California's eastern Sierra Nevada range and the Alabama Hills near Lone Pine, California. Lone Pine is 200 miles north of Hollywood, and has been used many times for location shooting since the early days of the movie industry.