DC9 ACFT ON APCH ENCOUNTERED AIRSPD LOSS OF 10 KTS TO VREF. WINDSHEAR WARNING ACTIVATED AND RPTR CAPT EXECUTED GAR RECOVERY WITH THE EXCEPTION OF USING MAX THRUST. RPTR BELIEVED THE PERFORMANCE OF THE ACFT WAS ADEQUATE WITH REDUCED THRUST; BUT IT WAS NOT ACCORDING TO COMPANY SOP. RPTR ALSO SURPRISED BY THE LOW WARNING THRESHOLD OF THE WINDSHEAR WARNING.

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AIRSPD LOSS AT 10 KTS (TO VREF) WITH NO VERT DEV FROM GS RESULTED IN 'RED' WINDSHEAR WARNING; THIS OCCURRED AT 300-400 FT AGL ON APCH TO RWY 24 GRB. INITIATED RECOVERY PER COMPANY POLICY EXCEPT THAT BY THE TIME THRUST LEVEL WAS AT GAR AIRPLANE HORIZ AND VERT PERFORMANCE WAS QUITE SIGNIFICANTLY POSITIVE SO THRUST LEVERS WERE NOT ADVANCED TO THE MECHANICAL STOPS. RETURNED AND LANDED WITHOUT INCIDENT OR FURTHER AUTOMATED WINDSHEAR WARNINGS. WINDS AT TIME RPTED 230 DEGS/25G35. ABSENT THE AUTOMATED WINDSHEAR WARNING ON THE FIRST APCH; I WOULD NOT HAVE INITIATED A RECOVERY. ACFT PERFORMANCE INDICATORS; WHILE VARIABLE; WERE WELL WITHIN COMPANY LIMITS FOR CONTINUING THE APCH. I BELIEVE MY FAILURE TO PUSH THRUST LEVERS TO THE MECHANICAL STOPS WAS A MISTAKE AND BELIEVE MY INEXPERIENCE ON THE AIRPLANE (MY 7TH LNDG AFTER IOE) TO BE A CONTRIBUTING FACTOR. HOWEVER; I WOULD SAY THAT I AM SURPRISED; EVEN SHOCKED; AT THE LOW WARNING THRESHOLD FOR THE WARNING SYS ON THIS AIRPLANE. I BELIEVED; AT THE TIME; THAT I WOULD HAVE PUT THE AIRPLANE AND PAX IN MORE DANGER BY GOING TO THE MECHANICAL THRUST LIMITS. AFTER THE FACT; I THINK I MAY HAVE BEEN RIGHT IN MY JUDGEMENT; BUT DEFINITELY NOT RIGHT IN MY LACK OF COMPLIANCE WITH COMPANY POLICY. I STILL DON'T KNOW WHICH IS THE GREATER 'RIGHT' BUT HAVE RESOLVED TO ERR ON THE SIDE OF POLICY IN ANY FUTURE EVENT.