His best showing against a top notch fighter was when he fought "Bad" Bennie Briscoe to a 10 round draw on November 18, 1975.
Another big win for Hart was the 10 round decision he earned over former Olympic champion Sugar Ray Seales on August 15, 1975.
He suffered a 9 round TKO loss at the hands of future middleweight champion Marvin Hagler on September 14, 1976.
Future light heavyweight champion Eddie Mustafa Muhammad knocked Hart out in the fourth round on August 26, 1974, and future middleweight king Vito Antuofermo KOed Hart in the fifth round of their March 11, 1977 match.
When Antuofermo did not wilt under the furious attack, Hart lost confidence and the tide of battle turned.