Hillman State Park lies within State Game Lands 117 and is open to hunting. It is not legal to use the trails during certain hunting seasons. For more info, call Hillman State Park, c/o Raccoon Creek at 724-899-2200.
From pgc.pa.gov/HuntTrap/StateGa…: "Riding activities are not permitted (except on Sundays or on roads open to public travel) from the last Saturday in September through the 3rd Saturday in January, and before 1 p.m. from the second Saturday."
Alternatively, you can add some mileage by riding the Haul Rd / Airport Connector by going left onto T820 after exiting the trail and looking for the trailhead immediately after the westward bend in the road.