This work presents an experimental approach used to evaluate the influence of binder constituents and solids loading on the rheological behavior and molding properties of irregular shape iron-based feedstocks used in low-pressure powder injection molding (LPIM). Thirty-six (36) different feedstocks formulated from one new in-development iron-based powder and different wax-based binder systems (paraffin wax (PW) with surfactant and thickening agents) were obtained for solids loading varying from 50 to 68 vol%. The viscosity profiles were experimentally measured at different temperatures using a rotational rheometer in order to quantify the threshold proportions of each ingredient in the binder systems, identify the best feedstock candidates, and calculate their moldability indices, which were finally validated using real-scale injections. Results confirmed that the best feedstock formulation was the one containing paraffin wax with 1 vol% stearic acid (SA) used as a surfactant, 2 vol% ethylene-vinyl acetate (EVA) used as a thickening agent, and 2 vol% carnauba wax (CW) used as a shrinking agent. An irregular shape iron-based feedstock with maximum solids loading of 58 vol% was successfully injected.