The Rifleman is similar to the European Skirmisher. It should not be used in frontal assaults or battles in the Fortress Age or later. In the real world they were known for their stunning accuracy and spartan lifestyle.
"The Klamath tribes of northern California and Oregon were among the last of the Native American tribes to fight the American settlers trying to take their lands. Late in the 1800s, they fought a war in very difficult terrain, holding off a much superior force for many months. In this bitter struggle, the natives proved especially effective with their rifles."