I seem to recall way back when that to find the foot poundage of an air pistol or air rifle there was a gadget, which looked like a metal quadrant on a stand, this had if memory serves me correctly two pendulums , when placed,, a short distance down range the object was to hit a paddle on one of them, this swung the pendulum initiating the second pendulum to swing on impact.
On the quadrant which was calibrated the second pendulum would stay at its most forward position , and the one that was hit by the pellet would return to its original position thus leaving a reading on the pendulum giving the foot poundage of the chosen weapon, am I correct and are these gadgets still around or does one now get the desired info from a chronograph? .