If you're using that, stop. Right now.
Treyarch recently nerfed the Ak-74u so it's more difficult to shoot at long ranges with (the grip is unnecessary, because the crosshairs were accurate without grip to begin with if you're running and gunning). You're better off using the Kiparis + extended mags + scavenger + SOH + and marathon/hacker/ninja because it has better Rate of Fire, accuracy, and power.
It's more powerful in all aspects (only downside being it normally has 20 rounds a clip, which is fixed by the extended mags attachment and where you'll usually run out of ammo, you'll recover it with scavenger (and you don't want to run out of ammo while using it, because you're in for the long haul in getting 11 kills). It is also less shaky than the 74u when it comes to aiming down the sights.
If you're playing on the wii version then I have no clue how effective this will be, but when I use it on my game I do much better than I do when I used that class you just mentioned