When you first start the battle, straight away through out one, only one, Rift Ripper/ Rift Inducer black hole. Having a level 4 or lower gun is ok, though it will be easier with a level 5 or higher gun. You only put out one black hole because if you have more than one, they will all go out faster. Since there is only one black hole, it should last for 4-10 rounds I think. Then everytime it dissapears, just put in another. Since there is ammo around you,your gun should last for atleast 50 rounds!!! Once you run out of ammo, you should put out megaturrents. They should last for a while too. Or you can buy more Rift Ripper/ Rift Inducer ammo and finish it. Also use your Flux Rifle/ Splitter rifle to defeat the bosses at the middle and at the end of the battle. [I am definitely not sure if it will work on your game but it sure worked on mine. GOOD LUCK]