I did some searching online and it looks like some people have used .20 BBs w/ this gun, but I haven't seen any results. Is it OK to use these rounds with this gun, or will it cause premature failure? The packaging recommends .12 for warranty purposes, but since I will be using this gun in outdoor areas I would rather use something that will hold up better to outdoor wind resistance, and occasional light breezes. Is there any firsthand experience?
To answer your question directly, because I'm pretty sure you already own this gun, you can go ahead and use .2g bbs in it. You could use .43s if you wanted and it wouldn't cause any harm. The extra weight of a .2g over a .12g won't affect the piston or nozzle in any way.