System 89 Background
Oehler developed the System 86 twenty-five years ago to meet needs of military proving grounds. High precision with long range were absolute needs. The ’86 delivers microsecond time accuracy and centimeter target accuracy when used with up to ten targets spread over ranges of many miles. The successor System 88 delivers similar accuracy for three targets spread over a few kilometers. The ’88 retained the precise GPS timing and the flexible radio network of the ’86.
Actual data collected with the System 88 has validated several premises and has provided new insight into the exterior ballistics of small arms.
- Exterior ballistic prediction models based on muzzle velocity are valid, if and only if, the predicted time-of-flight matches observed time-of-flight at long range.
- Accurate long-range predictions must be based on accurate measurements of long-range time-of-flight. Long-range behavior is primarily governed by time-of-flight, not distance traveled
- The combined barrel/bullet system must be considered. The ballistic coefficient and the drag function both depend on the bullet combined with a unique barrel.
Experience with the System 88 clearly demonstrates a total system for making long-range predictions. It accurately and reliably measures muzzle velocity and time-of-flight. These measurements are essential for accurate long-range predictions for the ammo and gun tested. Effects of the assumed drag function are minimized when the extended ballistic coefficient is determined by actual long-range time-of-flight measurements.
After using the instrumentation and studying the resulting data, we’ve determined realistic expectations of the accuracy required.
- Muzzle velocities should be measured to an accuracy of 0.1 percent. Skyscreen III units at three-meter spacing are adequate.
- Distance to target should be measured to an accuracy of 0.1 percent. Approved laser rangefinders used with appropriate reflective targets are adequate.
- The time-of-flight to target should be measured to an accuracy of 0.1 percent. This indicates millisecond accuracy over a one second flight time.
If the accuracy of your measurements is within the suggested one-part-per-thousand limit, then you can reasonably expect drop predictions within the range normally attributed to component variation of individual loads and the ability of the shooter.
Success of the System 88 now leads to the development of the System 89. Proving grounds may require multiple downrange targets, but most rifle shooters need only one target. One target requires only one radio link instead of the complex radio network. The microsecond timing accuracy of the ‘88 requires GPS synchronization. Millisecond timing accuracy is sufficient and the GPS is not required. We can retain the capabilities of the ’88, but at a lower cost.
The development of the System 89 is proceeding.
- The proven operator interface and software of the ’88 will be retained.
- The one downrange target can be either a square or a flyover acoustic target or it can be an impact plane for subsonic bullets. The impact plane is primarily for TOF measurements but may provide coarse target information.
- A special protocol is being developed to provide the required timing accuracy using the simple radio link.
The exact price is still to be determined. We expect to match the price of a new scope.