First of all you used a bad reference for the drawing. The back end of the bullet is out of focus and burred and your lacking alot of potential detail. Then there are some issues on how you drew the lighting on the bullet it doesn't particularly match your original. You have some differences in the shadow and the back part of your bullet isnt as convincing as it should be. Simply because your working with a bad reference.

Now you if drew the blurr with the image and studied that it would of been fine. But trying to correct faulty references isn't a good idea unless you have done the studies and know the knowledge ahead of time.