Abstract: The device (10) consists of a bar (12) of high explosive having a planisymmetrical groove (20) along one side lined with a hollow charge liner (28). A pair of backing charges (34, 36) connected by a bridging charge (42) are disposed along the opposite side of the bar. Each backing charge is separated from the bar by a gap (38, 40) which tapers towards the common longitudinal periphery of the bar and charge. The surfaces of the backing charges facing the gaps are lined with liners (46, 48). A linear initiating charge (54) is separated from the bridging charge longitudinally of the device by a gap (61). The facing surface of the charge (54) is lined with a metal strip (58) which, when the charge is detonated, is projected across the gap (61) to initiate the bridging charge linearly. A detonation wave then propagates from the bridging charge down each backing charge towards its peripheral region, projecting the liners (46, 48) across the gaps (38, 40) to initiate the bar.