With the help of a purpose-built pendulum machine, we studied the surface resistance of a ductile steel to impact indentation by hard α-alumina balls. The pendulum is equipped with a piezoelectric transducer which allowed measurement of impact impulses. In this way we could measure the mean contact pressure and the impact time directly. In the range of impact velocities used, the deformation regime is essentially elasto-plastic. We obtained the dynamic hardness-strain data for the steel AFNOR 25CD4 in this regime. We compared the results with some models and theories already proposed in this area of knowledge. We concluded that the experimental equipment used is very useful in single particle normal impact and in impact friction studies. However, very little experimental work has been done in this area using equipment like the pendulum machine used here.