Get your property surveyed and then post it. That is your first step. If you are basing your judgement on what you "think" is your property, just forget it.
Next, talk to your neighbor. Communicate to them that their late night gun shooting is disturbing you.
I would be very careful about accusing someone of poaching. That is what you are saying. Hunting after legal hunting hours and hunting on someone elses property without written permission are both examples of poaching. Poaching is a criminal act. Shooting at night probablly is not a criminal act where you are, just annoying.
Finally, I doubt that they are "hunting" with multiple gunshots being heard. If DNR were to roll up on my house at night after I've been shooting, I'll tell them to get bent. That being said, I have also talked to all of my neighbors, and they are aware that there could be some night shooting. I keep it to a minimum, as a matter of politeness. But there is no law against it.
Welcome to the country. Don't like shooting at night, move to the city. Wait, never mind there is probably even more shooting going on there at night.
