Internal Ballistics

Internal Ballistics has been a pretty popular topic lately, especially as people are becoming dissatisfied with the performance of current-generation airsoft guns and are looking for ways to improve their accuracy and consistency. The most successful attempt that I've come across used steel rounds and to look at the wear marks in the barrel. While this was a good first attempt, it doesn't give enough information aside from the bounce and roll locations. The proposed method of accomplishing these goals are attaching vibration/strain sensors along the outside of the barrel. With known sensor positions, the axial velocity of the bb can be extrapolated from the distance between sensors and the time between bounces. The radial velocity can be found by running a series of tests (probably drop tests) to relate the velocity of the bb with the response of the sensor. Once the axial and radial velocity are known, the trajectory of the bb inside of the barrel can be found to a reasonable degree of accuracy using some polynomial fit. The precision of this method is limited by the scanning frequency of the data acquisition module and the grid spacing for the vibration sensors.