Steel plates loosely mounted in frame, with neoprene pads between the frame and plates to better absorb the noise and impact from projectiles. The plates are inclined having laterally projecting tabs in openings defined by parallel steel side-walls. A containment chamber communicates with downstream ends of inclined plates by a transition area downstream of the inclined plates. Chamber has projectile impact boundary defined by laterally extending vanes or strips of hardened steel. End portions of vanes fit loosely in openings defined by the chamber side-walls. The vanes have beveled edges that abut one another so movement of adjacent vanes occurs in response to one of these vanes being struck by a projectile. Vanes are biased inwardly toward normal, or rest positions, but can move outwardly when impacted by a projectile. The number of vanes selected to establish angles of incidence for adjacent vanes less than 12 degrees in chamber.