Forces and Direction                                                                                                                                                                                                                                    The force released from an explosion when unconstrained is always perpendicular to the surface of the explosive itself. This means that it will spread out equally initially if the explosive is a perfect sphere. There are also shaped charges that use this property to their advantage to focus the force in a particular direction or area by enclosing it. A good example of this is a firearm. As you can see in the image on the left, since all but one portion of the explosive (The back of the bullet in this case) is covered, most of the force will be perpendicular to the back and sides, causing the equilibrium forces to push the bullet in the opposite direction. Also, due to conservation of momentum the bullet  will stay flying for a while and in turn is what causes the recoil to push back against you.