I have successfully modified a clip for a Maruzen Walther P99 airsoft pistol to accept co2 cylinders.  I can't test it for another ten hours, as some cold weld still needs time to cure.  I'm confident that it will hold air once a co2 cart is plugged in.  What I'm not sure of is what will happen the first time I pull the trigger.  I figure one of two things could go wrong.  The valve in the magazine, designed for lower pressures, will malfunction once released and either be damaged or allow much of the air to escape before closing.  Or, the blowback will occur with such force as to send the slide flying off the gun and drive it into my eye socket.  Anyone have any experience with this?  Am I the first person to try this?  Thanks. -Ed