The pilot departed Lawton, Oklahoma at 0902 local time on a flight to inspect mineral property. At about 0931, the pilot contacted Ft. Sill Approach Control and requested vectors to Lawton. He was instructed to fly a heading of 320 degrees. After flying that heading for about six miles, the pilot asked for and was given the Ft. Sill weather. Shortly after that, the aircraft entered a right turn to a southerly heading. When queried, the pilot replied he was in VFR conditions and turned intentionally. Earlier, the radar controller had received reports of a scud layer southeast of Lawton and assumed the pilot was VFR on top. The controller provided a heading of 260 degrees and advised this should take him into a clear area. At 0941, the aircraft return disappeared from the radar scope. The plane crashed southeast of Lawton in a wheat field on level terrain. It traveled about 300 ft after impact. An observer on a rescue helicopter reported a ceiling of 100 to 300 ft and visibility of 1/4 to 1/2 mile.