Boomerang is an acoustic system installed on military vehicles that is designed to detect relative shooter azimuth/range/elevation from incoming small arms fire. It performs passive acoustic detection and computer-based signal processing. Aural and visual alerts are used to 1) inform vehicle occupants that a bullet has passed within close proximity to the vehicle and 2) indicate the position of the shooter relative to the vehicle’s direction of travel. Boomerang operates when the vehicle is stationary or moving (no motion compensation) using a single, compact, mast-mounted array of microphones. The system is calibrated to detect infantry small arms. This calibration, however, does not preclude the system from detecting larger and smaller supersonic rounds. In this paper, we discuss the design, development, testing and production of 50 Boomerang I systems over a 65-day period in late 2003/early 2004. These systems were deployed during Operation Iraqi Freedom II with Marine and Army units. Feedback from operational units identified specific deficiencies and desired improvements that were incorporated into a system re-design effort, Boomerang II. The Boomerang II system has been extensively tested for performance and environmental fitness regarding RF compatibility with tactical radios (SINCGARS), heat, cold, shock and vibration. The US Army Aberdeen Proving Grounds conducted successful RF compatibility tests, road tests and 'live fire' testing. Summary results of open field 'live fire' static tests are presented as well as performance results on a remote-controlled HMMWV operating at 45 MPH.