I have a Ross also. It's in excellent shape and is .303. It, at first glance, appears "sporterized" ; however I found out that many were cut down while in use during the war and I even found a WW1 picture of a Canadianicon GI holding a rifle in the same configuration as mine in the trenches.
Mine has RCMP marking on the butt plate, which I found out is not uncommon either.