I just picked up a brand new M4 from the local gun shop. Went the next day to the range to fire it and every single round started to fail to eject.   I get home to inspect, and I notice damage as well as some weird rust or gunk all over the components...     For all new owners, check your gun prior to taking it out the range. Now its gotta go back for warranty service. The customer service rep had no idea what that substance was nor how the whole thing got chewed up. Spending this much