Colonel Gunn joined the CF in 1971 under the Regular Officer Training Programme. He attended Royal Roads Military College and le College Militaire Royal de St Jean, graduating with a BSc in Honours Physics from the Université de Sherbrooke.
Commissioned into The Royal Regiment of Canadian Artillery in 1975, he has filled traditional Regimental positions in all three Artillery disciplines (Field, Air Defence and Locating) in Canada and Europe. Command appointments have included Commanding Officer of the 129th Airfield Air Defence Battery, Commanding Officer of the 119th Air Defence Battery and Commandant of the Air Defence Artillery School. While commanding the latter he amalgamated the School with the Field Artillery School to form the Royal Canadian Artillery School, of which he was the first Commandant.
Staff appointments have included an operations staff position in HQ Canadian Forces Europe, a tour in the Directorate of Artillery, a stint as EA/Coord to the Director General Land Force Development, and Section Head in the Land Requirements Directorate responsible for Fire Support, Air Defence, and Reconnaissance, Intelligence, Surveillance and Target Acquisition issues. He recently completed duties as a Section Head in the Land Strategic Planning Directorate and was responsible for Army Business Planning and Performance Measurement. Col Gunn was promoted to his present rank in June 2002. He is now the Director of Land Requirements and was appointed the Director of Artillery.
In addition to his BSc, Col Gunn holds an MSc in Guided Weapon System Engineering from Cranfield University (Royal Military College of Science) and an MBA from the University of Ottawa. He is a graduate of the Canadian Forces Staff School, the Canadian Land Force Command and Staff College, the Canadian Forces Command and Staff College and the Gunnery Staff Course (Guided Weapons) run at the Royal School of Artillery, Larkhill, England.