Hamerli Air Magnum: no power

Hi all,

I bought my son a Hammerli 850 Air Magnum about two years ago which he absolutely loves. We used it today for the first time in 6 months (it was stored without a CO2 cartridge) and we barely got 10 shots off at full power before a precipitous drop in power: the BBs barely make it 20 yards before dropping. I've read that CO2 based weapons lose power in the heat. It was in the 80s today. Could that be the explanation or do I have a faulty unit?

Best, 

Mitch