AN ACR ACFT EXPECTED BOS RWY 27 ILS FROM ATIS. CLOSE-IN WITH A TAILWIND; ATC SWITCHED TO RWY 22L. AT 200 FT UNSTABILIZED THE CREW EXECUTED A GAR. ATC CLEARED ACFT FOR APCH TO RWY 27 CLOSE IN AND HIGH. CAPT TOOK THE ACFT FOR LANDING.

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AT THE END OF AN UNEVENTFUL TRANSCON; WE DESCENDED TO 6000 FT; 250 KTS HDG APPROX 090 AT ROUGHLY 6 TO 8 MILES NORTH OF BOSTON. ATIS HAD BEEN REPORTING RWY 27 ILS IN USE FOR THE PAST 4 HOURS. THE CAPT AND I HAD SET UP FOR AND BRIEFED THE ILS RWY 27. SINCE NO SPD RESTRICTION HAD BEEN ISSUED YET; I FELT 250 KTS WAS APPROPRIATE; SINCE A 7 TO 10 MILE FINAL IS COMMONPLACE IN CAVU. UNEXPECTEDLY; APCH ISSUED; 'EXPECT THE VISUAL RWY 22L.' WE BEGAN TO DIAL IN ILS FREQ FOR RWY 22L; PULLED THE APCH PLATE AND REALIZED THAT WE HAD A 20 TO 30 KT TAILWIND WITH JUST A COUPLE OF MILES TO GO TO THE LOCALIZER. THEN APCH ISSUED; 'TURN RIGHT TO 180 DEGS CLEARED FOR THE VISUAL TO RWY 22L; CONTACT TWR 132.22.' THIS TURN FURTHER SHORTENED THE DISTANCE TO THE RWY. I BEGAN TO SLOW TO EXPAND FLAPS AS QUICKLY AS I COULD; REALIZING THAT WE WERE VERY HIGH AND FAST FOR THIS APCH. I DISCONNECTED THE AUTOPLT AND BEGAN HAND FLYING. WITH THE GEAR EXTENDED AND AS MUCH FLAP AS POSSIBLE FOR THE SPD; I LOWERED THE NOSE TO TRY TO INTERCEPT THE GLIDESLOPE FROM ABOVE. THE CAPT RECOMMENDED GREATER USE OF SPD BRAKES BUT I WAS UNCOMFORTABLE WITH THAT SINCE I HAD LITTLE EXPERIENCE IN THAT CONFIGURATION IN CLOSE WITH SUCH A HIGH RATE OF DESCENT. THOUGH THIS WAS A VERY UNUSUAL SITUATION; IT STILL APPEARED THAT IT WOULD BE POSSIBLE TO ARRIVE IN THE SLOT CLOSE TO NORMAL PARAMETERS; AND I FELT THE CAPT WOULD CALL FOR A GO AROUND IF HE WAS UNCOMFORTABLE. AT APPROX 400 FT WE BEGAN TO GET 'SINK RATE' WARNINGS WHICH I EXPECTED GIVEN OUR HIGH RATE OF DESCENT AND 'GLIDESLOPE' WARNINGS SINCE WE WERE PASSING THROUGH IT AS I RAISED THE NOSE TO DECELERATE TO VAPP. AT APPROX 200 FT THE CAPT CALLED FOR THE GO AROUND. I CONFIRMED; 'GO AROUND?' AND HE RESTATED; 'LET'S GO AROUND.' I PUSHED TOGA AND RAISED THE NOSE TO STOP SINK. I CALLED FOR FLAPS 20 AND ADVANCED THE THROTTLES TO APPROXIMATE GO AROUND POSITION; BUT THE AUTOTHROTTLES WERE FIGHTING TO RETARD TOWARDS IDLE. IN THE HIGH DRAG CONFIGURATION; I DID NOT WANT SPD TO DECAY ANY FURTHER. TWR THEN CALLED FOR A LEFT TURN TO 140 DEGS AND I BEGAN A GENTLE TURN WHILE RETRACTING THE GEAR AND FLAPS TOWARD 5. IT WAS HERE THAT I THOUGH THE OVERSPD OCCURRED AS I WAS TASK SATURATED AND STABILIZING THE ACFT. TWR ISSUED 090 DEGS AND 2000 FT. I BEGAN TO FEEL THAT I HAD CAUGHT UP WITH THE ACFT; ASSUMING THAT WE WERE BEING VECTORED TO A DOWNWIND FOR A SECOND APCH TO RWY 22L. TWR THEN ISSUED; 'TURN LEFT 360 DEGS; CLEARED FOR THE VISUAL TO RWY 27.' LOOKING ACROSS I SAW THAT WE WERE ABOUT 3 MILES FROM THE APCH END; 2000 FT; 200 KTS CLEAN; ABOUT HALF MILE SOUTH OF THE RWY 27 FINAL APCH COURSE. AS THE CAPT COACHED; I TURNED IN TOWARD RWY 27 ALREADY GOING THROUGH THE FINAL APCH COURSE. AT THIS POINT THE CAPT REALIZED WE NEEDED MORE ANGLE OF BANK THAN I WAS USING AND TOOK CONTROL OF THE ACFT. WE SWITCHED PLT FLYING/MONITORING ROLES AND HE COMPLETED THE VISUAL LANDING.