The bullets you were trying to make are reffered to metal jacket bullets, the reason? They have a copper/bronze jacketting which takes the full explosion of gun powder easier than previous bullets, further more the bullet itself is usually smaller althought this is also determined by the caliber or mm further more at the base of the bullet there is a point where the hammer strikes causeing a spark this is called the setonator cap you can see it bevel out of the center of the bottom, that is the most important part of the bullet itself.
