When COL Payne is reprimanding PVT Johnson about her failing the drug test, she has her hat on. Members of the US Army do not wear hats indoors. When he's finished he salutes her and she returns his salute--that's backwards. She should salute him first and hold the salute until he returns it.
Sheriff Charlie Wade is armed with a Colt 'New Frontier' revolver, first introduced in 1961 by Colt as an updated version of the old Colt 'Peacemaker'. The events in the film take place in 1957 and 1958.