This paper addresses the problem of maximizing the altitude that can be reached by small, unguided rockets propelled with low-thrust engines. A physical–mathematical model of a launcher device using exhaust gas recovery to increase the initial velocity of the rocket is presented. A case study related to a small-scale model used in amateur rocketry competitions is described. The analysis shows the constructive parameters of the piston launcher that optimize the performance of the rocket. The best thrust profile of the available motorizations, which potentially include delayed ignition of the sustainer, is identified, as well as the optimal distribution of the masses between the stages. Finally, the possibility of further increasing the initial velocity with a piston launcher through the use of retention mechanisms to increase the pressure in the tube or through the use of auxiliary gas generators is investigated. The results show the considerable performance benefits of using a piston launcher.