James Montgomery was selected to represent Canada in trap shooting at two editions of the Summer Olympics. In 1920 he was fifth in the team event, alongside George Beattie, William Hamilton, Ben McLaren, True Oliver, and Sam Vance, and sixth individually. Four years later he won a silver medal with the Canadian team (Beattie, Vance, William Barnes, John Black, and Samuel Newton) and came in fourth individually after losing a bronze medal shoot-off with Frank Hughes of the United States. This team also came in third at that year’s British Championships. An R. J. Montgomery was also Ontario provincial champion in the doubles in 1929.
At the time of his Olympic appearances, Montgomery was involved in the produce export business and served as a manager of a local Grape Growers Association. At some point after 1924 he moved to the United States and became a representative of the Lowell H. Trumbull Produce Company of Detroit. This position him eventually led him to settle in Rio Hondo, Texas, where he purchased a farm and, in 1947, became mayor of the town, a position that he held until his death in 1964. While in the United States, he continued to win shooting championships and also became well-regarded as a sports fisherman.