A jet of material was observed exiting from the rear of the remnants of an initially semi-hollow explosively formed projectile, which perforated a finite thickness composite armour panel. The observation of this phenomenon was made by means of flash-X-ray photography at two different sub-millisecond times for a copper EFP that impacted the panel at above 2000m/s. The jet exhibited remarkably similar characteristics to what is typically observed for shaped charge jets for similar liner materials. Progressive necking was observed in the jet and the velocity differences between necked sections were characterized. Simulation of a similar generic event by the ANSYS Autodyn hydrocode showed that reverse jet formation is possible for specific EFP geometries and impact conditions. The relatively low velocities of the jet elements in terms of the laboratory coordinates, holds promise for the soft recovery of the jetted particles.