The film was written by Audie Murphy's friend Willard W. Willingham and his wife. Willingham had appeared in many of Murphy's films (playing Trooper Fuller in this one)
Audie Murphy's fee for this film was $50,000.
The eponymous repeating rifles are Model 1892 Winchesters, although they have brass-plated receivers, presumably to make them look like the Model 1866 "Yellow Boy" rifle, which would have been correct for this film set in 1868.
It was filmed in 1966 in Red Rock Canyon State Park (California) and Lancaster, California.
Audie Murphy's next-to-last film.