Abstract: A numerical study has been conducted using the explicit non-linear transient dynamic numerical code AUTODYN-2D to analyse the penetration and perforation of EN8 (AISI 1040) steel plate by the 5.56-mm L2A2 Ball round. The steel plate was heat-treated to two different hardness values and quasi-static tensile tests were performed to provide work-hardening constants for the Johnson-Cook constitutive model. A model of the bullet was developed using material data available from existing AUTODYN model libraries and parameters modified based upon the measured hardness of the bullet's individual components. The numerical results compared favourably with experimental trials where the bullet's residual momentum after target perforation was measured by means of a calibrated ballistic pendulum. The simulations provided some useful insight into the penetration mechanisms.