Primetake

High speed images were required showing the terminal effects of different AP rounds on metal plates, fired from a distance of 550m, There was 15 firings in 7 series of trials, all of which were required to be recorded. Trial site regulations meant that no-one could be forward of the rifle.

The problems to overcome were firstly, how is the camera to be triggered and secondly, how can the recorded shot be downloaded quickly and the camera re-armed. Automatic download and re-arm has always been a built-in function with Photron cameras.

However, due to the time between firings only being around 15s, the stored memory needed to be trimmed first before saving (this is normally done manually on the laptop) otherwise the download time would be too great. A unique way of triggering the camera had to be developed and in order for the shot to be trimmed appropriately, this trigger had to be generated by the bullet hitting the plate (T=0s). Pre-determined mark in/mark out points could then be set allowing for a fast download and re-arm, ready for the next shot.

With the help from Photron Europe Ltd, a custom impact trigger sensor was made. The impact sensor was clamped to the metal frame work holding the target plate. Upon sensing an impact/knock, it generated a TTL signal which triggered the camera (Photron SA-X2 mono high speed camera). Trimming points were set at just 100 frames before the trigger and 100 frames after. Using a connected laptop, the camera was armed and everyone retreated behind the rifle.

From this point onwards the process was fully automatic – rifle fired, bullet impact on plate detected, camera triggered, 200 frames saved to the laptop with a time stamped filename, camera re-armed ready for next firing, and so on. This whole process took about 12s. It worked perfectly and every firing was captured.