PLT OF BE200 HAS CLOSE PROX WITH P3 WHEN USING VISUAL SEPARATION.

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I WAS NWBOUND JUST E OF THE SAN JOSE; CA; ARPT; DSNDING FROM 5500 FT TO 4500 FT; WHEN THE BAY APCH CTLR POINTED OUT A P3 ACFT AT MY 10-11 O'CLOCK POS; ABOUT 2 MI; EBOUND; CLBING TO 4000 FT. I SAW THE P3 (WHICH PROBABLY JUST DEPARTED MOFFETT FIELD); RPTED IT IN SIGHT; AND WAS TOLD TO MAINTAIN VISUAL SEPARATION; AND CONTINUE MY DSCNT TO 1500 FT. AT THAT TIME THE P3 WAS QUITE LOW; CLBING SLOWLY; AND MOVING RAPIDLY FROM MY L TOWARD MY R. MY INITIAL ASSESSMENT WAS THAT I WOULD PASS WELL BEHIND THE P3; SO I BEGAN A RAPID DSCNT TO 1500 FT PREPARATORY TO MY LNDG AT THE HAYWARD; CA; ARPT. I CONTINUED TO SCAN THE AREA FOR OTHER TFC. WHEN I SAW THE P3 NEXT; IT WAS RAPIDLY BECOMING 12 O'CLOCK POS AND CO-ALT WITH MY ACFT. THIS SEEMED TO ME TO HAPPEN QUITE SUDDENLY; AND WAS TOTALLY UNEXPECTED BASED UPON MY INITIAL IMPRESSION THAT THE P3 WOULD PASS WELL IN FRONT OF AND WELL BELOW MY FLT PATH. IN ORDER TO INSURE SAFE SEPARATION; I ROLLED INTO A L TURN TO PASS BEHIND THE P3. THE P3 CREW SAW ME AT THIS TIME; AND RAPIDLY TRANSITIONED FROM A CLB TO A DSCNT TO INSURE SEPARATION FROM ME. THE P3 TOLD THE CTLR THAT I HAD BEEN 'CLOSE;' AND THE CTLR INFORMED THE P3 THAT I WAS MAINTAINING VISUAL SEPARATION. IN RETROSPECT; I SHOULD HAVE REMAINED AT 4500 FT UNTIL THE P3 WAS CLR OF MY ACFT TO THE E. HOWEVER I WAS RAPIDLY APCHING THE SEGMENT OF THE SFO CLASS B AIRSPACE WHICH EXTENDS FROM 4000 FT TO 8000 FT MSL. MY INITIAL IMPRESSION THAT THE P3 WOULD PASS WELL IN FRONT OF; AND BELOW ME; WAS BASED UPON MY FIRST SIGHT OF THE ACFT SOME DISTANCE AWAY. AS WE CAME CLOSER; THE GEOMETRY OF THE SIT PROVED ME WRONG. FROM MY SEAT THIS WAS NOT OBVIOUS UNTIL THE 2 ACFT WERE MUCH CLOSER THAN THEY SHOULD HAVE BEEN. IT SEEMS TO ME THAT THE CTLR MIGHT HAVE NOTED THE CONFLICT EARLIER THAN I DID; AND STOPPED MY DSCNT; OR THE P3'S CLB. I SUSPECT THE CTLR WAS BUSY; AND WAS TRYING TO EXPEDITE ME. I WAS AMAZED AT HOW LITTLE TIME I HAD TO REACT ONCE I DECIDED THAT I MUST TURN TO AVOID THE P3. I HAVE ONLY COME CLOSER TO OTHER ACFT ONCE OR TWICE IN 34 YRS OF FLYING. I WAS VERY UNCOMFORTABLE WITH THE SIT; AND I AM SURE THE P3 CREW WAS NOT HAPPY EITHER. I USUALLY AVOID THIS AREA BECAUSE OF THE HVY TFC. I WILL DEFINITELY AVOID IT IN THE FUTURE. I WILL NOT RELY QUITE SO MUCH ON BUSY CTLRS EITHER.