I'm not sure that it works like this. That is, I'm not sure if there are guys with guns on your property, that you can arm yourself, go out there after them, shoot them or even point a gun at them, and then claim it was self defense. Some states require you to run from intruders even in your own home - and if your state has castle doctrine(stand your ground laws), that usually only applies to a home and curtiledge (like a garage, fenced in yard, etc).
Hopefully law enforcement will support a property owner in an obvious situation of self defense, even if they approached the trespassers. I suppose everyone knows to consult your own state laws and maybe ask an attorney before deciding how to handle those situations.
In Idaho you have to fire a warning shot......doesn't have to be the first shot.