This contribution addresses size and boundary effects on wave propagation, fracture pattern development and fragmentation in small scale lab size specimen for model blasting. Small cylindrical specimens are center-line loaded by linear explosive charges and supersonically detonated. Using elastic wave propagation theory and fracture mechanics it is shown that the type of boundary conditions which prevail at the outer boundary of the cylinder control the extension of borehole cracking and fragmentation within the body of the cylinder. In the case of a composite cylinder where the core is of a different material than the mantel, the level of fracturing and fragmentation is controlled by the separation of the interface which in turn depends on the relative diameters of the core and the mantel. The most important parameter though is the ratio between the length of the pulse (space-wise or time-wise) and the characteristic dimensions of the models, i.e. in this case the diameters of the core and the mantel. The plate like specimens is either a single cylinder or consists of a possibly dissimilar core and a mantel. The core is always a cylinder but the mantel can be either a cylindrical or square tube. In all cases the blast-hole and explosive is in the center of the specimen.