A new model for rigid projectile perforation of target plates is compared with experimental results for many combinations of spherical projectile diameters, target materials, target plate thickness´ and impact angles. In most cases of importance the model predicts the required perforation energy of a projectile with reasonable accuracy. For a few cases (hard targets in combination with soft projectiles and impact angles greater than say 45°) the experimental results show that the assumption that the projectile is rigid is not valid, and then the model predicts perforation energies that are too small in comparison with the real energies required for perforation. This also agrees with the model, since the projectile deformation requires additional energy in order to achieve perforation. In other cases involving subsequent perforation of several thin and soft plates the material from the perforated plates is accumulated in front of the projectile, which is a situation not covered by the model Materials that are used for shields against projectiles are normally "hard and brittle", and for such materials the model appears to be directly applicable, which specifically means that the "static" yield strength is used to characterise the target material. For materials that are "ductile" the application of the model seems to require a "dynamic" yield strength, which is a few times larger than the "static" yield strength. It is suggested that the difference between the static and the dynamic situations depends on the mobility of dislocations.