WOW!
There is a headshot hack but I SERIOUSLY doubt that you would need to use it.
It's actually pretty simple to get headshots with R weapons.
It just all depends on your reaction time and skill level.
Judging by the games that I have played with you, you have fast reaction time and moderate skill.
You could do it.

WAR_MONGER and I played a game with R weapons in the Canyon.
It was a 2 v 2.
Me and him vs 2 random people.
We both got ALL headshots.
Not a single nade/regular kill.

That's pwnage.
;)