A CIRRUS PLT IS UNABLE TO STOP AND RUNS OFF THE END OF THE RWY; RESULTING IN A PROP STRIKE.

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ON APCH TO PDK; I WAS ASKED TO MAINTAIN 170 KTS TO THE OM. AT THE MARKER; I WAS ASKED TO MAINTAIN 150 KTS. WX WAS RPTED TO BE 600 FT OVCST WITH GOOD VISIBILITY. WHILE SHOOTING THE ILS RWY 20L; I DSNDED TO MINIMUMS ON RWY 20L (6001 FT). I WAS JUST ABOUT TO DECLARE A 'MISSED APCH' WHEN I SPOTTED RWY 20L. AT THIS POINT; TWR SWITCHED ME TO RWY 20R. I SAW RWY 20R AND ACCEPTED NOT REALIZING RWY 20R ACTUAL LENGTH (3744 FT). I HAD TOO MUCH AIRSPD DUE TO REQUEST TO MAINTAIN 150 KTS. BY THE TIME I SET ACFT ON RWY 20R (WHICH HAS A HUMP IN THE MIDDLE); I COULDN'T SEE THE END OF THE RWY. AFTER PASSING THE HUMP; I HAD SLOWED SOMEWHAT; BUT NOT ENOUGH TO STOP BY THE END OF THE RWY. RWY 20R WAS WET FROM HVY RAIN. THERE WAS A LOW CLOUD ON THE APCH END OF THE RWY WHICH OBSCURED MY VIEW UNTIL I REACHED ABOUT 300 FT AGL. MY ACFT WENT OFF THE END OF THE RWY. I SAFELY TURNED MY PLANE AROUND TO ENTER THE TXWY. AT SOME POINT; THERE WAS A PROP STRIKE WHICH WAS ONLY NOTICED WHEN I ARRIVED AT THE ARPT TO LEAVE AND WAS ADVISED THAT THERE WAS DAMAGE TO MY PROP BY LINE SVC. I BELIEVE THE INCIDENT LIKELY OCCURRED WHEN THE PLANE WAS ENTERING THE TXWY FROM THE WET AND SOGGY GRASS. IN RETROSPECT; THE INSTRUCTIONS GIVEN TO ME WERE MORE THAN EITHER THE PLANE OR I COULD ACHIEVE. I DON'T BELIEVE THAT I SHOULD HAVE BEEN ASKED TO SWITCH RWYS UNDER THE ABOVE CIRCUMSTANCES.