In addition to building three main patterns of straight-pull bolt action rifle for the Canadian military and the commercial market, Sir Charles Ross also experimented with self-loading rifles. Starting with a standard Ross Mk III, this experimental rifle has a gas piston and trigger to allow automatic fire and a very neat forced-air cooling system. A one-way rather mechanism (now broken, unfortunately) spins the fan when the bolt cycles, pushing air into a barrel shroud similar to that of a Lewis gun. This rifle was most likely made in 1915 or 1916 with an eye to a military light machine gun or automatic rifle contract – which never happened.
Thanks to the Canadian War Museum for providing me access to film this Ross for you!