R1ghty, are you using an aftermarket inner barrel and mid-heavyweight Bastards?
Okay so if anyone is running/trying to run CO2 and has magazines leaking out the top... I found a solid fix!
http://gasguns.info/forum/viewtopic....=1737&start=30
Worked on my worst leaking mag, and I'm going to do up the other 11 and run them all in near-zero temperatures next week. I'll report back with performance. I'm just using whatever material of o-ring I can find in the right size, but from a quick search butadiene seems like the best for this application. If I don't get a good lifespan out of the current o-rings I will probably retrofit the magazines with butadiene rings from here:
http://www.plasticservices.com/HoseFittings/orings.htm