Mpls. Police Fire Live Ammo To Calibrate ShotSpotter System Minneapolis Police will conduct a calibration test of its ShotSpotter technology Monday night in two precincts. According to police, testing will occur in the Folwell and Central neighborhoods, respectively in the 4th and 3rd precincts. The Folwell testing starts at 7 p.m., and the Central testing starts at 8:15 p.m. In each test, 25-50 shots will be fired for calibration purposes. Guns will be fired by officers in to a bullet trapping system, which safely absorbs bullets fired at close range.