I received a Model 99 awhile ago. Its in good shape but well used made in 1956. I took it to range emptied the magazine worked fine. It was dirty inside so I took the stock of and cleaned everything up. I didn't take anything apart. Now when I eject a shell the next shell starts to feed and jams. If a move the lever back, ( like a double pump the shell feeds. It doesn't seem to make a difference if its the first or last shell. Any suggestions?