In an effort to extend the modified explosive component water gap test [1-3] defined by the NATO standardization agreement (STANAG) 4363, several countries have investigated the shock sensitiveness of confined lead and booster components having a diameter less than 5 mm [4-8]. A pentaerythritol tetranitrate (PETN) based acceptor pellet is chosen as a reference with a height and diameter of 3 mm. The height of the steel confinement is equal to the one of the HE pellet and the wall thickness varies. A 1-mm thick wall makes the component more sensitive (larger water gap). As the wall thickness is increased to 2-mm, the gap increases a lesser amount. A decrease in sensitivity is observed with a 3.5 mm thick wall (smaller water gap). This decrease of the water gap has been reproduced experimentally. This unusual behavior remains puzzling and does not allow the test to be extended for small components. This work presents the numerical simulations performed with LS-Dyna in 2D axi-symmetrical and 3D wedge configurations, using an ignition and growth model [9] for LX-16 (96% PETN, 4% FPC 461) in order to evaluate the shock sensitiveness for a confined HE acceptor.