The trick was that many of his kills were from a distance of 50 m or less, not like today where snipers shoot people even from like 3 km away. So not using a scope really made him practically invisible even for the remaining soldiers who where next in line.
I also recall reading that he wet the snow around his firing position, so as to prevent plumes of snow getting blown up into the air by the exhaust of each shot.
The trick was that many of his kills were from a distance of 50 m or less, not like today where snipers shoot people even from like 3 km away. So not using a scope really made him practically invisible even for the remaining soldiers who where next in line.
I also recall reading that he wet the snow around his firing position, so as to prevent plumes of snow getting blown up into the air by the exhaust of each shot.