[Penguin]

You can keep your electric power, but just build in a small selanoid into your gun with a propane tank on a remote line... and just vent the gas out the ejector or through a little nozzle under the barrel. You'll still get a loud kind of pop but you'll retain your electric power. I think that would be neat. It will also mask the mouse-sex noise an AEG already makes.

I know that companies use propane powered machineguns in movies to save on the cost of blanks (saving private ryan for example)