A non-isentropic, quasi-unidimensional model has been developed to predict particle velocity during cold spray metal deposition processes using mixed propellant gases. The model has been validated under several process conditions and propellant gas compositions. System temperatures ranged from 200°C to 400°C, system pressures varied between 19 and 65 bar, and propellant gases included pure helium, pure nitrogen, and helium/nitrogen mixtures. Aluminum particles (Al6061, 40 micrometer average size) were accelerated in a 120 mm polybenzimidazole (PBI) nozzle using a high pressure cold spray system. A good agreement was observed between predictions and direct velocity measurements using the HiWatch HR (Oseir, Inc.) diagnostic system. Predictions of the current model were compared with tri-dimensional CFD simulations as well. Both model and actual measurements showed that a mixture with 20% nitrogen in helium led to a decrease in the particle average velocity by only 7% compared to a full helium spray. Such a result reflects potential cost savings without significantly affecting the quality of the deposition. A MATLAB based graphical user interface (CONiCAL: Cold spray Nozzle CALculator) was implemented to facilitate the usage of the model for practical manufacturing purposes such as nozzle, powder, and propellant gases selection.