Either cut the amount of heavy ammo for machine guns in half, or double the amount of rockets that are obtained from heavy ammo crates. I get one magazine for my rockets and 2 magazines for my machine guns. That equals to 2 rockets total or around 70 machine gun bullets. If a machine gun takes 4 or 5 bullets to kill someone, you can optimistically get around 10 kills from one crate if you miss a bunch of shots with a machine gun, while usually only getting about 4 maximum kills from rockets. Its going to need a change