I'm also interested. I think the primary restriction is if firearms are allowed to be discharged for that purpose within your town at all. Many towns require you to be "outside town limits," if the town has a local ordinance prohibiting discharging a weapon. Beyond that I can't cite a specific law, aside from using common sense and sufficient safety precautions.
I know the town I grew up in enacted a really crappy law that pissed a lot of people off. This is a tiny town of 800 residents, and many had very large properties and many were farmers. The town completely banned the use of firearms for any purpose, and effectively banned hunting. Bow and arrow were also restricted, requiring 10 acres or more for it to be legal to shoot a bow at all. Anything less is considered unsafe.
Banning hunting like that for people who have 50 acre farms really ticks me off, and I'm not a hunter. Hunting is a lot of peoples' passion. The deer population is out of control as it is anyways. There are more deer in North America now than there were when Columbus sailed here.
Bows and arrows are unsafe on less than 10 acres of land? Give me a break! I grew up on 6 acres with woods on all sides of the property. Really stupid.
Also the law was written in such a way that it effectively applied itself to BB guns and probably Paintball guns too. Punishment was something like a $7500 fine and 5 years in jail for a second offense. Freaking liberals.