The featherweight was the second-lightest class, allowing boxers of up to 126 pounds (57.2 kg).
Norton of Great Britain Poillot gave Gunn strong competition in the first round, but Gunn knocked the Frenchman down shortly before the first bell.
Constant, while never giving Ringer a serious chance of defeat, fought well throughout the bout.
Gunn and Morris both won their bouts in the latter ends of the contests, with Roddin and Ringer giving stiff competition in the early rounds but not able to keep up with the winners the whole way through.
Gunn fought Morris back and forth, with the 38-year-old veteran coming out on top following a strong final round.