I ran the Call of Cthulhu adventure "No Man's Land", changing the adventure background from Americans in the "Lost Battalion" to Canadians soldiers during 2nd Ypres (the first use of poison gas adding nicely to the horror).
Of course, this meant inflicting the Canadian-made Ross rifle on the players. A militarised version of a finely made and highly accurate sporting rifle, it did not work well in the mud and dirt of the trenches. For example, the straight-pull bolt was often worked only by kicking it. In the game, the jam number was so high players quickly abandoned them for whatever German Mausers or British Lee Enfields they found lying around.
Again, the Ross apparently wasn't a terrible weapon, it was in fact considered a superiour marksman's rifle in its own right. Also bear in mind the Ross was adopted because of a prior British refusal to sell or licence the Lee Enfield for Canadian use or production, and some kind of rifle was needed.
Tony