This paper aims through several numerical studies to highlight some effects of layering plates in ballistic protection. The possible increase in perforation resistance by varying the material properties of the plates, the individual plate thickness (the total plate thickness is constant) and the stacking of individual plates in a double-layered target when struck by blunt and ogival nose projectiles has been investigated. This was done by conducting non-linear finite element simulations of the perforation process using an experimentally validated numerical model and an explicit finite element code. These studies are difficult to carry out experimentally due to the many materials and thicknesses involved and computer-aided design is thus an attractive approach. The numerical design indicates that it is possible to considerably increase the overall ballistic protection level by using double-layered plates and a proper design. Some of the most promising designs were then selected for experimental validation. The experimental tests gave completely opposite results than the computer-aided design, and the reasons for this will be discussed in some detail.