the very first gun you unlock is probably the best. try playing the game before coming to conclusions
from what i see, the first guns are usually all around type weapons (m4a1), later in the game you get guns that are more suited to a specific playstyle (m14/ak47) or possibly a better all around gun (acr).
this is usually what i see in cod. imo its a good system until you get a gun like the type 95 early in the game. this is the main problem, getting good guns to early. if the type 95 wasn't until lvl 65+, it would be more balanced out by the fact that you don't get it until late game.