The Marksman (1953) Wayne Morris, Elena Verdugo, Frank Ferguson

Mike Martin becomes a deputy United States marshal in early-day Texas because of his almost unbelievable marksmanship. (That he has a rifle with a special scope doesn't hurt anything.) He hates the thought that he has been hired as a killer instead of a lawman but his superior, Marshal Bob Scott, sets him straight. For years a master gang of rustlers has raided government grazing lands and Lieutenant-Governor Watson orders Scott to get them. Scott, disguised as a prospector, is killed when he spots the outlaws deep in the Sangre de Christo range. Head of the rustlers is rancher Champ Wylie and his gang includes his foreman Santee and a crack gunman, Kincaid. Visiting Wylie is his novelist niece Jane Warren.