The mathematical support for calculation of external ballistics for subsonic weapons is described taking into account external factors for the tactical optical-electronic simulator for small arms "Inhibitor" developed at the Institute of mechanics UdmFRC UB RAS and at Computer facilities department of Kalashnikov ISTU jointly with JSC «Kalashnikov» Concern». The tactical and technical assignment is given for ballistic calculation of the trajectory and point of hit of subsonic simulators of PM weapon and GP-25 with the laser emitter of the targeting point taking into account external factors: position of the sighting bar of all types of sights (mechanical, optical, night) with the procedure of their preliminary sighting (transformation of coordinates of the laser spot into coordinates of the visual targeting point), features of the mounted trajectories of the GP-25 (air pressure drop with the height of the trajectory), air temperature and pressure, wind force, ballistic scattering minus the hardware error of the sighting point recorder (geometric subtraction of independent random errors). Mathematical models of external ballistics implemented in the software relying on the aiming angle of the weapon simulator, the initial speed and ballistic coefficient of various types of ammunition in real time in the simulator coordinate system make up a ballistic trajectory in order to solve the “meeting problem”. Results of software tests for the error in the calculation of ballistic trajectory characteristics are given. It was concluded that further research and development of electronic shooting simulators were promising thanks to the improvement of computing tools and the development of software libraries in order to increase the accuracy of simulating external ballistics of simulators taking into account many external factors, expand functional networks and reduce cost and, therefore, increase competitiveness.