well... i ran C02 a long time ago on one of my LP spyder (when i wasnt rich enough to run HPA), tank wasnt even anti-siphoned...a regular 12oz java tank and the reg(AIM SHOCK REG) would freeze up and mess the rings up... what i know is that c02 messes up orings.
if the manual (i hope we all read it before we go out and play) says "HPA or compressed air only" theres a reason for that........WARRENTY COVERAGE!!!
come on!!! someone else said "if u got money to go out an buy a $1200 marker...then u diffenetly have $150 for HPA tank!!!"
even the less fortunate players can buy one for cheap!!!