well im very close to unlock all the weapons and i have some play time with most of them (but i mostly play with the m27 IAR /m4a1) so from what ive gained until now i can say a few things:
1. the KH2002- played with it once but i didnt realyl ike it that much so i never used it again. its a burst fire weapon with a low recoil and nice firing rate if you have good trigger finger(which i do not
2.the Famas is 1 heck of a weapon! it has the highest firing rate(1000 RPM) in the Assault section , same damage(25) but its horizontal recoil is very high so only go with it for close quarters combat(operation metro/siena crossing/grand bazaar ) because in the medium-high range its almost impossible to get a kill without shooting the whole MAG, to balance out its fire it DICE gave it one of the longest reloads so always make sure youre under cover when you reload, to shorten that reload time always reload when you still got bullets in your mag , it gives yo 1 extra bullet and the reload is faster.btw the famas is great for hipfire so if you put on him a foregrip and silencer you'll probably rock youre enemy's world
3.the m416 is great when youre on the russain team and you cant use the m16a4, it has almost the same stuff only a little lower firing rate and a wee bit more recoil.
4.the m16a4 is probably the most fun weapon to use in the game , it has low recoil,high firing rate and one of the shortest(if not THE shortest) reload speed, when you reload with buletts still in your mag it will take less then 2 seconds to reload so never be afraid to reload with that weapon.
also a great option for a weapon in the assault class are the AEK-971/F2000. both of them are what called "OverPowered" with super high firing rate(900/950RPM) but both of them take alot of time to reload so again find cover and always switch to your pistol when youre in a fire fight and youre in a need for a reload with them.
thats pretty much it