Don't fill them clips too high, give them bullets room to breathe
They are talking while filling clips after all
He’s probably using an Uzi, which are notorious for double feeds when overloaded, causing a jam. This line implies that BIG is a little rusty. He hasn’t had to resort to violent retaliation lately, so he really needs to focus or he could screw up (foreshadowing).
This implies the bullets are alive (a technique called Anthropomorphism) which is ironic as they will soon be used to kill someone.
To help improve the meaning of these lyrics, visit "Somebody Gotta Die" by The Notorious B.I.G. Lyrics and leave a comment on the lyrics box