87 Machine Gun Chronograph and Scoring System


Users have asked for a modern system to measure muzzle velocity, rate-of-fire, and target scoring for automatic weapons. The venerable Oehler Model 82 has done this for thirty years, but it runs under DOS, communicates via RS-232, and uses an obsolete 9-pin printer. Oehler’s new system runs under Windows XP or later, communicates through an USB port, writes test reports in .pdf format and exports both the results and raw data as an Excel file. Operator interface is similar to the Oehler System 85. The System 87 now includes a firing simulator built into the package. The simulator provides simulated velocity screen signals along with simulated microphone signals for system set-up, operator training and performance verification. The microphone signals form a predefined group at the target. The battery powered simulator is electrically independent of the measurement system.

In the System 87, the muzzle velocity and targeting functions are concurrent during the burst, but the two functions remain independent of each other. This robust system reliably gives both velocity and target information during the test. The system can measure velocities and rate-of-fire without using a target; it can measure target performance without using velocity screens; or it can measure ROF using only one microphone. Times-of-flight and exact correlation between velocities and impact point can be computed from recorded raw data in the leisure of post-processing.

The System 87 measures muzzle velocities and rates-of-fire using photoelectric screens near the muzzle. The system records the time of each response signal from each screen. All recorded times are referenced to the time of the first recognized event. The system also records the arrival of the Mach cone of each bullet at each of four down-range microphones The microphones are arranged at the four corners of the target square and the scoring area is the circle within the square. The system computes the apparent impact point of each round using the observed arrival times, the air temperature, and expected projectile velocity at the target. Both the procedure and the microphones have been proven for over thirty years with the Oehler Model 82.

The System 87 records up to 10,000 rounds per minute through a target of 1 meter diameter, 6,600 rounds per minute through a target of 2 meter diameter and 4,400 rounds per minute through a 3 meter diameter. Precision is approximately 0.15% of target diameter. For each round, it provides epoch time at muzzle start screen, muzzle velocity, ROF at muzzle, epoch time at target, ROF at target, and target coordinates. The system will accommodate up to 400 rounds in a burst. Results are displayed at the operator’s computer and are automatically stored as a .pdf report. Test conditions along with both processed and raw data are automatically stored to an Excel file.



Sample Test Windows



System 87 Back Panel



Click here to download System 87 Brochure in .pdf format.