[Masterless]

If it's getting really cold after only 5 shots and then running out of gas it may be venting too much gas with each shot. Lubricate everything, and work it all to make sure the lubricant penetrates everywhere it needs to go. Having said that, it sounds like a problem with the mag. Make sure the seals are lubricated and the valve is functioning properly. Like Kozzie said, sometimes they just don't. It frosts me when an expensive mag fails right out of the box, but almost every problem has a solution. There are tons of ideas on what to try online. Work some Goggle-fu and you should find your answers.