The ability of a ceramic to resist penetration by projectiles depends, in a coupled manner, on its confinement and its mechanical properties. In order to explore the fundamental inter-relationships, a simulation protocol is required that permits the microstructure and normative properties (hardness and toughness) to be used as input parameters. Potential for attaining this goal has been provided by a recent constitutive model, devised by Deshpande and Evans (DE) [2008, “Inelastic Deformation and Energy Dissipation in Ceramics: A Mechanics-Based Dynamic Constitutive Model,” J. Mech. Phys. Solids, 56, pp. 3077–3100] that incorporates the contributions to the inelastic strain from both plasticity and microcracking. Before implementing the DE model, various comparisons with experimental measurements are required. Previously, the model has been successfully used to predict the quasistatic penetration of alumina by hard spheres. In the present assessment, simulations of the dynamic penetration of confined alumina cylinders are presented as a function of microstructure and properties and compared with literature measurements of the ballistic mass efficiency. It is shown that the model replicates the measured trends with hardness and grain size. Motivated by this comparison, further simulations are used to gain a basic understanding of the respective roles of plasticity and microcracking on penetration and to elucidate the phenomena governing projectile defeat.