Don't know if you guys noticed, but if you ignore the Nexus and focus on killing his spawn you get tons of ammo. Started the fight with only two slots of ammo and finished it like this...
DeadSpace
Spawn Kill pics
ImGoingToHellForThis
ImGoingToHellForThis
ImGoingToHellForThis
ImGoingToHellForThis
funny
ImGoingToHellForThis
ImGoingToHellForThis
ImGoingToHellForThis
ImGoingToHellForThis
eyeblech