M20K PLT RETURN LAND AFTER EXPERIENCING MECHANICAL ENG FAILURE.

Narrative

I WAS 10 MI FROM THE ZZZ1 ARPT AT 2500 FT WHEN I HEARD A POP IN THE ENG. A QUICK SCAN OF THE INSTS HAD ME DOING A DOUBLE TAKE OF THE OIL PRESSURE GAUGE. THE OIL PRESSURE WAS READING ZERO. I HEADED STRAIGHT FOR THE ARPT (ZZZ1); CALLED THE TWR; AND DECLARED AN EMER. 1 MIN LATER; THE AMMETER SHOWED A 10 AMP DISCHARGE. MORE NOISE FROM THE ENG. TWR ASKED; 'DO YOU WANT EMER EQUIP STANDING BY?' I REPLIED 'YES.' I AIMED THE AIRPLANE 1/2 WAY BTWN THE BEACH AND THE ARPT. I CALLED THE TWR AND TOLD THEM WE MAY LAND ON THE BEACH. AT 2000 FT OF ALT; WITH 4 MI OF GLIDE RANGE; I TURNED AWAY FROM THE BEACH AND DIRECTLY TOWARDS THE ARPT. THE ENG STARTED WITH A STEADY GRINDING NOISE TELLING ME IT WAS TIME TO SHUT IT DOWN. I REACHED FOR THE MIXTURE CTL AND SHUT DOWN THE ENG. I DOUBLECHKED THE GEAR DOWN; AIRSPD; ALT AND ENERGY LEVEL. ALL WERE GOOD AND THE SHORT APCH WAS STABLE. THE LNDG WAS UNEVENTFUL; NOT MY BEST; BUT FAR FROM MY WORST. ON THE GND; I TRIED TO TURN THE PROP -- IT WAS NEARLY FROZEN. I CHKED THE OIL. IT HAD 5 QUARTS AND IT SHOULD HAVE 6 1/2. NO OIL LEAKS. LOOKS LIKE SOMETHING ON; OR NEAR; THE OIL PUMP BROKE AND FROZE THE ALTERNATOR AS WELL. I BELIEVE THERE WAS A SUCCESSFUL OUTCOME DUE TO THE FACT THAT I MADE AN IMMEDIATE DECISION TO TREAT THE ZERO OIL PRESSURE READING AS A REAL EMER. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT THE CAUSE OF THE ENG FAILURE WAS DETERMINED TO BE A SHEARED MAGNETO IMPULSE COUPLER PIN WHICH DROPPED DOWN INTO THE ACCESSORY CASE JAMMING THE OIL PUMP AND ALTERNATOR DRIVES.