Hollow cylindrical charges of PE4 were detonated. The charges had masses of 0.16 to 0.49 kg and a length to diameter ratio of 1/1 to 1/6. The circular hollows were of diameter 0, 0.01, 0.02 and 0.04 m. The charges were detonated from one end. The results showed that provided the correct ratio of charge mass, charge length to diameter ratio and distance are maintained the peak overpressure and impulse remain constant. This means that it is not necessary to know the size of the hole to predict the peak overpressure and impulse in the radial direction. For PE4 the peak pressure, P, is given by P = -251 (M(L/D)1/3R-3)2 +1677 M(L/D)1/3R-3 and the impulse, I, by I = 150 M2/3 R-1. M is the charge mass, L the charge length, D the charge diameter and R the distance from the charge
