[BloodSport]

run them stock for a bit, they will work on Propane and I know several people who never upgrade theirs. Down the road you may find that your plastic slide(s) will crack and need replacement either by a new stock one or a metal kit. As for internals honestly you really only need (suggested) to change your loading nozzle to a reinforced one (Guarder makes them) to take the higher pressure from the propane as the stock one will most likely crack. Also ensure you use the AI silicone oil when filling your mags to prevent the o-rings from drying out. Otherwise all other internal upgrades are pretty much to increase your ROF or FPS depending on what combinations and parts you use. I've got a fair mixture of upgraded (some slide only) and stock pistols and they are all run on propane on a regular basis.