Just play advanced mode!
In case you don't know what that is: Â it's a mode in which you start off only with secondaries and the more kills you get the more weapons become available to you - one at a time for every 3 or 4 kills on average...
Btw, why don't more people play advanced mode?
I mean, everytime you hear people think of more and more game modes and then when the next version comes out, they play the new game mode for the first month and then it becomes completely obsolete...