A bullet is a very small lump of soft metal (probably already fragmented into little pieces when it hit) trying to wedge between two pieces of steel against the force of the propellant. It is going to get smeared. A force can be an applied force, or an object can experience a force as a result of acceleration. You feel an example of this in an elevator, when the elevator goes from not moving to going downward (a small acceleration), you feel “lighter” for a moment – the force between your feet and the floor is apparently smaller.