We report a synthetic and theoretical study of the solid solution SnxFe4-xN (0 <= x <= 0.9). A previously published ammonolytic synthesis was successfully modified to achieve the metastable nitrides in phase-pure quality out of many competing phases. As TG-DSC measurements show, the thermal stability of the nitrides increases with increasing tin content. The SnxFe4-xN series of compounds adopts an antiperovskite-like structure in space group Pm (3) over barm. Various experimental and theoretical methods provide evidence that the iron substitution by tin exclusively takes place at Wyckoff position la and leads to a Vegard-type behavior of the lattice parameter over the compositional range, with an expection for a small internal miscibility gap around Sn0.33Fe3.67N of unknown cause. For highly tin-substituted iron nitrides the composition was clarified by prompt gamma-ray activation analysis (PGAA) and determined as Sn0.78(3)Fe3.22(4)N0.95(3) evidencing a fully occupied nitrogen position. Magnetic measurements reveal a linear weakening of ferromagnetic interactions with increasing tin concentration.