The Ross was a straight-pull bolt action rifle used by the Canadian military in the early stages of World War I. It had several interesting features and strengths, despite ultimately being a failure as a front-line infantry rifle.
The Ross used a set of helical interrupted threads in the bolt sleeve and bolt body to cause the bolt to rotate when opened or closed. While clever, this had the side effect of making the rifle very susceptible to dirt and fouling. It didn’t take much gunk in the threads to prevent the action from cycling.The other minor little issue was that it was after a detail stripping it was possible to reassemble the bolt in such a way that it would close but not lock, and shoot back into your face upon firing. This issue, while dramatic (and a big concern to the few poor schmucks who discovered it), was not as much of an issue in actual use as it has been made out in more recent discussion of the rifle.
The Ross was actually quite popular as a sniper rifle – it was capable of excellent accuracy as long as it and its ammunition were kept clean. H.M. McBride gives a very positive description of it in his book “A Rifleman Went to War” (highly recommended if you haven’t read it).
However, by 1916 the Ross was being replaced by the Lee Enfield, and remained in service only with some sharpshooters. It was also used as the basis for the Huot light machine gun, but those never made it into production. For the folks interested in learning more about the Ross, we have a copy of a Canadian 1907 manual covering the MkI and MkII versions of the gun (crossposted as always on the Original Manuals page in the Vault):
(1907) Ross MkI & MkII manual (English)