Abstract Properties of fragment clouds produced by hypervelocity perforation of metal plates have been experimentally investigated. Replica model techniques have been applied. Targets consisted of steel dual-plate systems. Projectiles were hard metal spheres of tungsten carbide (3 mm, 7 mm and 10 mm diameter, HRc 79) and steel spheres (6 mm and 12 mm diameter, HRc 63) at velocities ranging between 2.3 km/s and 4.5 km/s. Cloud expansion velocities have been measured by means of in-flight flash X-ray photograph series. Maximum and minimum fragment velocities at front and rear side of clouds have been determined. From impact crater patterns on witness plates, and X-ray photographs of debris clouds, projectile and shield fragments have been identified. It has been found that plate perforation holes and debris cloud parameters scale geometrically for 6 mm and 12 mm diameter steel and 7 mm and 10 mm diameter hard metal spheres. For the 3 mm diameter hard metal spheres only the maximum debris cloud velocity vrmax scales; all other parameters show deviations, indicating non-uniformity of the plate perforation process at different plate thicknesses. The shape of the inner part of debris clouds of steel spheres is different from that of hard metal spheres, caused by the density difference. For steel spheres the debris cloud shape is a convex lense, the shape of the hard metal fragments becomes in the rear nearly hemispherical. Increasing of the impact velocity causes an increasing of the expansion velocity and a flattening of the debris clouds.