The recently published two-step ammonolysis reaction giving access to phase-pure GaFe3N has been reinvestigated. Thermochemical calculations show that a high-temperature route is necessary to avoid the formation of the competing GaN phase. Compared to the prior study showing a Vegard-like behavior (that is, a linear correlation between lattice parameter and elemental composition), improved X-ray analysis using Mo K alpha(1) radiation in combination with density-functional theory calculations reveal a more complicated behavior of the lattice parameter within the entire Ga5Fe4-xN series. The new finding originates from the magnetic properties, and the change in the magnetic ordering with increasing Ga content from ferromagnetic gamma'-Fe4N to antiferromagnetically ordered GaFe3N, as observed from susceptibility measurements, is reproduced by different theoretical spin-alignment models, that is, a systematic evaluation of several antiferromagnetic spin orientations. Nonetheless, all structural models are based on the favored atomic ordering for GaFe3N, explainable by the strong affinity between iron and nitrogen.