You are talking about military sniper team who`s role is to eliminate targets at long distances. Spotters in those teams indeed carry advanced optics and ballistic computing devices to provide all the necessary info for a sniper. Btw the spotter is also a sniper and usually carries a sniper rifle on his own, but less powerful). IIRC those weren`t present in armies of 1970th century, instead platoons usually included a designated marksman who was using a special rifle (usually called Designated Marksmanship Rifle) like M14, g3sg1 (which sprite is used in game) or SVD.
Here in xenonauts we have a special task force more like swat/specnaz, who usually deploy in urban area where there is no need for sniper teams (great spotting distance) and utilise lighter sniper rifles like svu/psg/scout tactical etc.
Taken from here: http://www.xenonauts.com/category/equipment/
I was rejoiced when i read this as there never were any sniper rifles in X-COM. But i was rather disappointed to see no increase in sight range when using precision rifle. I can imagine soldiers using M14s or special modification of M16 for better accuracy, but that G3 sniper gun with a scope of no less than 8x magnification just makes me crazy!