The problem is most people don't understand how to correctly fill TM mags. They expel air as you fill with propane to get rid of any air pockets. People think there's an issue with the fill valve and don't keep filling until liquid propane spits out of the filler. People not getting through 30 rounds simply haven't filled the mag enough. The green gas mod is optional and yields higher gas capacity in turn also increasing magazine pressure which will bump up the fps a little as well. There's no need to do the green gas mod, however there's really no reason NOT to do it too. It only gives you better performance over all.