Some Airsofters make the horrible mistake of buying the 0.20g BBs from a Walmart or Canadian tire for their high quality gun. Constant use of these low quality BBs will end up killing your gearbox.
Notice how pieces of the BBs are getting everywhere? That’s because they are not seamless. If you look at the photos below, you can tell the difference between the top photo and the bottom photo.
So be careful when buying BBs from your local store. Buy your BBs from licensed Airsoft websites and stores.
UPDATE: Recently, while using Bio BBs, I’ve noticed that if any jam when firing, it can actually shatter the Bio BB. Unless your prefered field requires Bio BBs, it would be better to use normal BBs rather than risk any internal damage.