Container (10) is generally cylindrical except for a longitudinal concave groove (11) extending along its entire length. Upon explosion, the contour of this groove (11) results in a focussing effect on the wall material due to the oblique angle at which the expanding cylindrical detonation wave front impacts upon its inner wall. This produces the forging of a rough rod-like projectile (11.sub.1) which, being coherent, maintains its velocity and consequently travels much further than the randomly shaped projectiles (10.sub.1).