it's just mouse accel and a combo with a flick shot
also bf3 snipers love dragshotting, except they don't use mouse accel
examples here
http://www.youtube.com/watch?v=m82WKId9Gws&hd=1&t=1m18s
or just some good mouseaim and a bit of flicking from raysteinerz
http://www.youtube.com/watch?v=RdXOEAtQXqg&hd=1
quakers shud play bf3, it requires a lot more mouseaim than quake.
I have 67% sniping acc in bf3, mad?
http://www.youtube.com/watch?v=tWGABeuUce0&hd=1
that's me, but don't compare me to the two above videos, those are montages >:|
that was just 1 game from me
bf3 teaches you mouse flicking good if you practice with snipers.
quake live doesn't really ever require you to do that, but ofc I do that.
CS also teaches you good reflex practice.
k1llsen seems to be one of the few players who practices his flickshots consistently.