If properly controlled, impact of micro-sized particles can be used as a machining process at very small scales.  Impact of an abrasive particle can be used to remove material.  Conversely, impact of a small projectile with a component made of a compatible material can be used to add to the component.  Implementing this concept requires being able to repeatably produce well-controlled impact events.   We present the results of a detailed computational fluid dynamics analysis of a projector designed to fire small pellets at supersonic speeds.  Internal flow during the firing event produces very large transient pressure gradients which must be carefully shaped to launch the projectile accurately.  In cases where the projectile is abrasive, its path must be controlled using transverse pressure gradients, since contact with the sides of the sides of the barrel or the nozzle could abrade them in a way that would unacceptably degrade performance.  Analytical results are compared with experiments using a compressed air-powered test device firing spherical projectiles.  The correlated analytical model is then used as a stepping off point for exploring more advanced designs.