Lately seen on youtube how ppl absolutely rock with assault rifles, SMG, and automatic pistols. And the main reason - they using gamepads.
It quite understandable gamepad need some degree of auto-aiming just so it would feel to horrible for them. At the same time M+KB obviously don't need autoaiming at all. But that leads to a problem where gamepad user have much easier way to fight the recoil, due to auto-aiming. Where M+KB doesn't have that.
Sniper rifles and shotguns are just fine when you use M+KB. But for full automatic weapon game really need to some sort of reduction to recoil, when game detects usage of M+KB