G&G CM M16 Carbine firing problems.

[MWatson]

Greetings,
I am very happy with my G&G CM M16 Carbine, I fire in bursts most of the time and i'm not too trigger happy. The problem is that some of the BB's just go off course a few of the BB's fired will not even reach where the other BB's do.
What is the problem, could it be the hop up?

Thanks for the help,
Matthew.

(couldn't think of what to search on the forums just incase you are frustrated with people not using that function)