The present study investigates numerically the assessment capability of the GHBMC M50-P with regard to behind armour blunt trauma (BABT) by applying impact loading with approximation of 3D surface of the armour back face displacement (BFD). The body armour consists of a hard-ballistic plate (9 mm silicon carbide and 10 mm ultrahigh molecular weight polyethylene, UHMW-PE) and a soft-ballistic component consisting of a 40-layer aramid fabric vest. The finite element model of the ballistic vest was applied to the GHBMC M50-P thorax using a novel forming simulation. A load case from previous experiments was selected where no penetration of the plate occurred (7.62 mm x 51 armour piercing projectile). For the approximation of the 3D surface of the BFD, the last layer of UHMW-PE at its maximum deformation was transferred from Ansys-Autodyn into LS-DYNA. For the evaluation of the BABT, the Viscous Criterion, the Blunt Criterion and the maximum strains in the impact area were used. The evaluation was performed at two locations:​ mid sternum ribs levels 3-4 and rib bone cartilage junction area at level 4. In both cases, the obtained probability of AIS2-3 injury was exceeded and the maximum strains indicate multiple fractures of the ribs or sternum.