Very little.
Randolph Scott alone is enough to make a good movie, but here he has a superlative script performed by some of the best actors Hollywood has ever had, including the excellent Bruce Cabot, a wonderful Charles Kemper, and two lovely ladies who look surprisingly like each other (at least here), which is good because they are supposed to be sisters: Barbara Britton and Dorothy Hart, two great actresses.
Mr. Scott, a genuine gentleman, used to pooh-pooh the notion he was an actor, but in "Gunfighters" he gives not only one of his best performances, but a great performance by anyone's standards.
He is alternately subtle and obvious, showing just the right emotion and attitude called for by the script, by Alan LeMay, who knew a thing or two about westerns.
Mr. Scott has a lot of help in this powerful story, with the above and Forrest Tucker, rather quietly effective as the hired gunman, and Steven Geray as Jose in an intelligently funny role (so many westerns had very unfunny funny roles), as well as so many great atmosphere and minor players, such as the ubiquitous Hank Bell, as usual uncredited.
"Gunfighters" is not only one of Randolph Scott's best movies, it is a great movie, one of the best I've seen lately, and I've been watching a lot of them recently. I highly recommend "Gunfighters," and can even highly recommend the print at YouTube. Enjoy.