A plug for insertion into a blast-tube exit cavity of a gun-blast diffuser comprises a plug front surface, a plug rear surface, a plug side surface that extends between the plug front surface and the plug rear surface, a body, comprising a polyurethane foam, and a substrate, coupled to the body and comprising a conductive nonwoven fabric, impregnated with a polyurethane matrix. The plug front surface of the plug is formed by the substrate. The plug rear surface of the plug is formed by the body. The plug side surface of the plug is formed by the substrate and the body.