I just bought an Ion off craigslist and the guy said he had co2 so i could dry fire it to show it worked but he showed up with an empty tank so i wasn't able to fire it. I know i should have just left but it was such a good deal an ion with tons of extras for $60. Well anyways, when i screw in the tank it sometimes leaks co2 out of the barrel or it doesn't fire even after i made sure i had the settings were right for firing. i have no clue what is wrong with it. it sounds like it isn't getting pressurized when i try to fire it. Can someone please help?