Ok, now i'm preparing short footage from recent matches.
the fact how i perform high HSKR is easy, as you said, just aim at your head like in R6S or CSGO
that's for same reason why i'm using SCARH mostly (high accuracy and damage)
as you can see in recent report, i didn't aim at head with AEK cuz it has low accuracy then i realize there's no mean i aim at head. (following reports)
https://battlelog.battlefield.com/bf4/battlereport/show/1/996742215828400448/416813006/
https://battlelog.battlefield.com/bf4/battlereport/show/1/996757694559185216/416813006/
seeing bullet spread, with scar-h, m16 and CZ, there's great meaning aiming at head for getting more kills, so i do.
the numbers are not quite ridiculous compared with Accuracy (17%Acc and 42%Head with scar, Pros have like 25%Acc and 25%Head or so)
so overall, it's the way how i'm playing bf4, experiments and trial.
that's also how i had played when i was in competitive scene in bf4; maybe 3 years ago?