There's a couple factors that can add to someone's effectiveness with sniper rifles. Each rifle has its own invisible Aim Assist stat. For example, Her Benevolence has an AA of 55. New Monarchy's Violator 12 has an Aim Assist of 27. Icebreaker? 50. Patience and Time? 65. Then you have the actual scopes. One of the most popular seems to be Ambush (x4.5 zoom), but that actually reduces your Aim Assist by 5 or 10. I don't remember how much exactly, but the compensation seems to be the highest Stability of all scopes. Shortgaze (x4.5 zoom) increases AA by around 20 I think, and the short range Longview (x5 zoom) increases AA by at around 30. Then you have the perk Hidden Hand, of course, to add even more AA on top of those two factors.