Complex sentence: Coburn became well known in the 1960s and the 1970s for his tough guy roles in several action and western films, first primarily with Steve McQueen and Charles Bronson in the John Sturges films, "The Magnificent Seven" and "The Great Escape".
Split into simpler sentences: Coburn became well known in the 1960s and the 1970s for his tough guy roles in numerous action and western films. He first appeared with Steve McQueen and Charles Bronson in the John Sturges films, "The Magnificent Seven" and "The Great Escape".