L12 assault rifle level - seems impossible

BurningWreck

I can take out a few enemies and the drones, but there are so many enemies that I get overwhelmed every time while I reload. I upgraded to a level 5000 assault rifle but it's still not enough. I have completed everything else in the game. This level is all that's available. There needs to be an explosive barrel near a big group of enemies so I have a chance!