That was probably the tappet spring. When you reassembled, there should have been a black piece with the air nozzle on the front. This is called the tappet plate, and it moves the air nozzle along the cylinder head, which allows a bb to enter the chamber. If you don't have the tappet spring, the plate won't reset properly and you will have feeding problems. When you crack the gearbox, there should be a small post almost directly under the cylinder head, and a small hook thing on the tappet plate. You need to reattach the spring to this part. Also, before you go any further, go to
www.airsoftplayers.com and find the gear box tutorial.
