Just watching some of my sniping footage in pvp (in between practice of eye level in patrol) and had to slo-mo some clips cause I'm surprised I even landed them. I realise there's aim assist, but one particular shot I looked way too far off to the left and got a headshot. Actually I just reviewed the footage even slower and it appears as though, while being under fire, the slight flinching while in scope "allowed" me to get a headshot on him. IE. I must have pulled the trigger just as I was being flinched and got the headshot anyway. My gun has unflinching, but I remember it saying that it's just reduced flinching with the perk.