Best Primary?

I have played halo since halo 2, although I really got into it after halo 3, and I am a pretty decent player with a 1.5 ish k/d on average.
Then this game comes out (which I love) and i am doing pretty bad in multiplayer.

So i need tips to get better, the most important being what is the best primary weapon? I’m not concerned about the storm rifle/suppressor, more of the carbine, light rifle, battle rifle, and DMR

I heard that the dmr is the best, but i haven’t gotten to try it yet.
So, what primary should i use?
EDIT
I actually have tried the br and im not really likin it, just doesn’t feel right.