You should call the police. Do not say there is someone hunting on your land you call them and say this their is a man with a gun near my barn I am in fear of my life, they will come. Trust me they have to come. I promise when the first hunter get's arrested and he will be arrested for at the very least trespassing he will tell his buddies and the word will spread like wildfire. It could very well solve your problem. Also, an alternative, if they are parking on your land have their vehicle towed. Under your no trespassing signs place a sign that says all violators vehicle will be towed at the expensive of the owner. Find their vehicle talk with a local towing company find one who will be willing to tow them off your property you might have to sigh a wavier so they will be able to tow them but call them up have them come get there vehicle. Hit them where it hurts the most their pocket book they will get the hint and stop hunting on your land.