As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FLIGHT, THE PILOT REPORTED HEARING A SLIGHT KNOCKING IN THE ENGINE AND NOTED A 20 PSI DROP IN OIL PRESSURE. A PRECAUTIONARY LANDING WAS MADE WITHOUT INCIDENT. COMPRESSION CHECK REVEALED NR 3 CYLINDER LOW AT 50/80. CYLINDER REMOVAL REVEALED NR 3 PISTON SKIRT BROKE WITH 2 INCH BY 3 INCH PIECE LOCATED IN OIL SUMP OF ENGINE.