What are the laws on shooting on private property in PA. I'm sure basically every town has a law against discharging in city limits. What about counties?

My parents have about a dozen acres near New Wilmington, my Dad seems to think he can shoot on his property, but he doesn't because he "likes his neighbors". I asked him if he was in any city limits and never gotten a strait answer (something to do with recent renumbering for 9-1-1 calls of addresses ect. ect.)

The reason I ask is he has a huge ground hog (or whatever sort of creature) problem and has hinted at taking his ,22lr to get one or two of them. I doubt he will do it (Mom wouldn't let him she loves the fury animals), but I'd like to know if it is, in fact, legal or not.

I realize this probably hinges on him being inside the town/city limits, but assuming he is outside of them. With all the Amish around and horse poop on the roads I don't think a couple of .22lr shots would bother anyone, but who knows.