Played for 2 weeks already, rank Elite 3 in MP but still struggling.

What gun do you guys use? Saw people said AK117 and AKS is good but I can't seem to get used to it. Sometimes I use AK117, and a bit later I suddenly feel like don't know how to use it.

I rotated and used M4, and 5-6 games later I feel like I've never use the gun before.

Probably (actually am) a noob, but I'm not that consistent in using any weapon.