Bumb.
1) Depending on ammo crate cover, when alone waiting for teammates, I'll wait until I take on an enemy rusher, when I know my teammates are on their way. Confident I can defend the crate, if not, nick em up enough to make them easy pickings.
2) When rushing enemy crate, I'll do my best to take them out, or grab it quickly in order to deny them.
1a) Getting Heavy distribution throughout my team gives us an advantage.
2a) Taking "enemy" crate, depriving them of heavy, puts them at an disadvantage.