Introduction. The development of small weapon and structurally similar products, their use for criminal purposes force forensic science and practice to make adjustments to the forensic classification system of firearms over and over again. Theoretical analysis. In forensic ballistics, firearms are classified according to their purpose, type, method of production, barrel length, barrel channel device, number of barrels, etc. By the method of manufacture, groups of factory, artisanal and improvised firearms are distinguished. At the same time, the system of signs developed by science for the self-made manufacturing method is not effective for all cases of expert research. It is the expert practice that gives the reasons for this statement. Empirical analysis. The paper examines the practice of expert research into submachine guns, that are structurally similar to the 9 mm K6-92 submachine gun (Armenia) and are manufactured as part of criminal arms production, as well as Strelkov submachine guns chambered for 9–18 mm. Individual items had the corresponding weapon attributes (hallmarks, number designations, etc.). The weapon production format, assessed as home-made, is characterized by the choice of simple design schemes, the operation of automation, the prevalence of a cartridge sample, simple manufacturing and assembly techniques, and low quality weapons. Discussion of results. The author proposes introduction of a public law attribute to the system of evaluation criteria of a method for producing firearms – its legitimacy. Its application creates the conditions for covering all cases of the production of firearms known to science and practice, the correct assessment of its method of manufacture, and the selection of an appropriate expert methodology for resolving issues related to classifying an object as a firearm. Conclution. Taking into account the results of the study, there are reasons for supplementing the varieties of improvised firearms known to forensic ballistics with a group of weapons manufactured in industrial plants that are not legalized by central government members.