So I got my first AR. It is the bushmaster C-15. I was changing the plate at the but stock last night to put a plate for a single point sling on it. I was very carefull to watch the spring. My wife said something to me and I turned and must of flicked it with my thumb as that thing went flying. So I need to get a new spring. Well I was pretty pissed that I did this and grabed the rifle and must have squeezed the charging handle and it released. I did not have the stock on at that point and one little pin at the end came out as well as soemthing else becase I can hear something in the rifle. I will break it down tonight to see what it is.. My only problem is I dont know were the pin came from. It is very small. any help or direction would be appreciated. I do not have a book or anything on were everything goes. so any recomendations on that would be great too..