As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING THE TAKEOFF ROLL, THE PILOT EXPERIENCED A SEVERE VIBRATION. THE PILOT ABORTED THE TAKEOFF AND SHUT DOWN THE ENGINES. AN INSPECTION OF THE AIRCRAFT REVEALED THAT A FEATHERING COUNTERWEIGHT ON THE LEFT PROPELLER HAD FAILED, DEPARTING THE AIRCRAFT AND DAMAGED THE SPINNER AND OPPOSITE BLADE. THE SEARCH FOR THE COUNTERWEIGHT IN THE SURROUNDING AREA HAS BEEN UNSUCCESSFUL (X).