Wow. If you have one that "actually" feeds and functions flawlessly, consider yourself lucky! They have been know to be problematic. If memory serves me, it's a faulty spring tension on the feed tube. On that note, don't bend or lose the feed tube. They are kinda hard to find and replace.
I assume you didn't get a manual with it, so check this out. There is also a web site dedicated to the rifle.
http://www.nylonrifles.com