The title "sharp shooter" or "riflemen" as used by antebellum militia companies was largely honorific. There was no assurances that the "sharp shooter" or "riflemen" militia company was equipped with rifle muskets. It was, in the words of John B. Gordon in describing his own company which he wanted to be called "Mountain Rifles," largely waxy poetic (they became the Racoon Roughs instead). Sharp shooter was indeed two words and it was sometime later that the germanic conjugation into one word was adopted. BTW, "sniper" was coined before the War of 1812 but didn't really enter the American lexicon about the time of the Boer War or World War I.