Gil Henderson took up shooting at the age of 16 and honed his skills while serving in World War II. He began competing at the provincial level in the early 1950s and became Ontario champion in the single and handicap trapshoot in 1955. He became Canadian national champion in the doubles and all-around in 1957, repeating that feat the following year. He competed at the 1958 World Championships and the 1960 Summer Olympics, but was eliminated in the qualifying round of the trap competition in the latter. He later served as team manager for the Canadian trapshooting delegation to the 1974 Commonwealth Games and as an administrator for the shooting team at the 1976 Summer Olympics. A member of the Brampton Gun Club, he was inducted into the Brantford and Area Sports Hall of Recognition in 2010. Outside of sport shooting he was a well-known conservationist and philanthropist and as a youth worked in the mechanical contracting industry.