How about a matrix of 2 mm square plates, each row and column carrying a slightly different voltage, but having some hard insulating substance between that can resist a pellet strike. A pellet strike would very briefly make a circuit between adjacent plates. The voltage would be proportional to the distance along along the x and y axes, and the position of a strike could be plotted from the voltage recorded across the plates hit.
Baked, or half-baked?
“We are too much accustomed to attribute to a single cause that which is the product of several, and the majority of our controversies come from that.” - Marcus Aurelius