my $0.02
some people have a knack for these things. in UT, i can get a headshot from very far away with an enforcer(when the headshot mod is on) and i don't cheat. i'm just accurate and i have played it enough i know how to get the kill. give me a sniper rifel and i won't even come close to their head
some people have a skill with one weapon, and one manuever, maybe fir3 is just really good at jumping with the mp5? besides, when it comes to accuracy, you can sometimes guess where the computer will decide to put the bullet and counter for it. i could do that in rainboq six often enough, so why can't it happen in CS? and i'm not supporting or accusing anyone(as i have no place to do so) just giving some food for thought 
some people have a knack for these things. in UT, i can get a headshot from very far away with an enforcer(when the headshot mod is on) and i don't cheat. i'm just accurate and i have played it enough i know how to get the kill. give me a sniper rifel and i won't even come close to their head