Canada used the Ross Rifle during World War I. Designed by Canadian inventor Sir Charles Ross, it was a straight-pull bolt-action rifle chambered for .303 British ammunition and adopted for Canadian military service in 1905.
The rifle performed well in target shooting, but battlefield conditions exposed serious weaknesses. Its long design, close manufacturing tolerances, lack of reliable primary extraction, and sensitivity to ammunition quality made it vulnerable to jamming in muddy trench warfare. Soldiers also discovered that the bolt could be dangerously reassembled incorrectly.
Canadian troops carried the Ross in the early years of the war, including during the Second Battle of Ypres in 1915. The Canadian Expeditionary Force gradually replaced it with the more dependable Lee–Enfield. The Ross was then largely relegated to training duties in Canada and Britain, where it helped free Lee–Enfield rifles for front-line use. The United States also received some Ross rifles for training, but Canada was the country that adopted it as its principal service rifle.