I disassembled my new 15 (per the included directions) to clean the shipping oils for the first time. As I was pushing a cleaning rod with cleaning patch through the barrel from the end of barrel I noticed something fly out of the other end of the barrel. Is there some plug in the barrel in the chamber end for shipping? My wife and I looked for 30 minutes and couldn't find anything. I have watched disassembly videos and I have all the parts shown.