Few yrs back I took a run of the mill 1917 No 1 Mk III Enfield to the 600 yds line at Winona and shot a 47/50 with issue v sights, at a 15 inch Bull off the elbows. All ORA guys, and me, were surprised at the accuracy of these old warhorses. Yes it was windy.
Larry Fish, Dean of service rifle shooting, now 91, told me that there was a technical reason once explained to him, on how/why the Number 1's were so accurate at 600 yds-1,200 yds. But the reason he could not quite figure out, however he and other Canadians used No 4's to 600, No 1's beyond and won most of the world's silverware,and that was what mattered.