Could, or would there be any reason to use more than one of these
Two possible reasons for using a rifle of the Colt Stoner AR15/M16 design might be that the AR15 rifle design allows the rifle to be disassembled by simply pressing two pins attatching the receiver/barrel assembly to the lower trigger housing/stock assembly, allowing for easy maintenance and a reduction in overall length by approximately one-half. Since any telescopic sight or other optical sighting equipment remains mounted to the upper receiver/barrel unit, there is no loss of sight zero requiring readjustment of the sights after reassembly.
That design feature also allows a lower trigger group with a target or match trigger assembly to be fitted with various different upper receiver/barrel configurations, ranging from different calibers, silenced barrel versions, and many different barrel length/sighting configurations. I expect it's unlikely that a sniper or sniper team is swapping AR15 upper receivers between engagements, but it's possible.
