A mortar system includes a launch unit that comprises a mortar ignition cartridge provided with a flashtube. The flashtube incorporates a ring-like nozzle that is positioned within the flashtube, which acts to restrain the motion of the black powder pellets as well as to choke the flow of the resultant combustion products. The nozzle separates the flashtube into two compartments: a flashtube venting chamber and a pellet combustion chamber. The mortar ignition cartridge combustion chamber acts as the product-gas venting area of the flashtube. The combustion of the black powder pellets essentially takes place in the pellet combustion chamber. The present design modification improves the overall performance of the mortar system.