Why not upgrade the slide on the TM and not use green gas? Propane has been found to be the primary ingredient of Green Gas, plus additive lubricants and scents. If you buy a propane adaptor and add silicone oil to the propane can, you can have virtually no cost in running a gas gun.
To add to your question, I wouldn't really trust a KJW too much. They lemon rate is higher than KSC and their mags are known to be faulty. So between those two Id take KSC but even still Id rather have a TM with a metal kit. This makes me miss my FMU TM 226
