Open air range ba?
Per PNP Circular 107 (22 Feb 1973):
5 foot width minimum (per bay, apparently)
Other requirement specs therein listed are:
-8 foot depth minimum from grade or berm-top
-total length not exceeding the height of the backstop.
-The backstop is to be either a natural hill or cliffside,
or else a concrete wall no less than a foot thick and fifteen feet high.
hth,
-horge