The influence of transverse shear effects, rotary inertia and the boundary conditions on the dynamic behavior of rigid perfectly plastic beams subjected to projectile impact at midspan is studied. Theoretical solutions for a perfectly clamped and a simply supported beam are presented. Numerical results are given for a rectangular and three wide-flanged I-beams of varying spans. For the particular range of parameters examined it is found that rotary inertia does not affect the response in a significant way. However, shear effects are very important for the particular beams considered, being more pronounced in wide-flanged short I-beams. In particular the maximum lateral displacement can increase substantially due to shear effects, showing that a bending only solution neglecting shear can lead to erroneous results. It is also found that shear effects are slightly more important for short simply supported beams than short clamped beams, but for large spans they are essentially independent of the support conditions.