Originally Posted by Styrak
If you're going to use Co2 mags on a stock TM gun, change the plastic slide to a metal one (and probably the barrel to metal as well). Even then, Co2 will be harder on the internals and they will wear out/break faster.
I did a little research into this (propane/GG vs CO2). To clarify Styrak's comment, CO2 is compressed at a higher pressure level in a cartridge cylinder vs propane. Higher pressure results in harder slide blowback and subsequent return. The harder kick results in higher stress on the internals and increased wear on externals. So, you *can* use CO2, but it would likely shorten the life of the stock components. Also, at the end of the day, you would need to pull the CO2 cartridge from the magazine, regardless of its fill condition, for storage. There is also the higher cost factor of CO2 cartridges compared against propane (not GG).
Upgrading components would be one way around this issue, but usually those upgrades would be performed to improve accuracy and reliability. In the end, most folks, from what I gather, use either GG or propane, with the majority using propane for cost reasons.