I just bought the land so these guys probably don't know that there are new owners. I saw them on game cameras and the land isn't posted yet.

If I saw guys with rifles on my land AFTER posting I'd try to get vehicle tags, then report them. If I can't find a vehicle I would approach them, ask if they saw the signs, and then tell them that they are trespassing. All with a concealed sidearm ready to go.