FLC OF MLG HAD ANNUNCIATOR AND MASTER CAUTION LIGHT ON TKOF ROLL. AT 100 KTS CAPT ABORTED TKOF WITH 4000 FT OF RWY LEFT AFTER STOPPING.

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ON TKOF ROLL AT WASHINGTON NATL (WX 1000 OVCST 2 MI R-F) AT 100 KTS; ANNUNCIATOR AND MASTER CAUTION CAME ON SHOWING FORWARD ENTRY DOOR OPEN. ABORTED TKOF WITH NO INCIDENT. RETURNED TO GATE AND MAINT DISCOVERED THAT FORWARD ENTRY DOOR WAS NOT LOCKING PROPERLY AND THE DOOR HANDLE HAD ACTUALLY POPPED OUT OF LOCKED POS DURING TKOF ROLL. IT WAS AT THIS POINT THAT I RECALLED RECENT SIMULATOR SESSION WHERE WE HAD BEEN SPECIFICALLY INSTRUCTED NOT TO ABORT FOR A MASTER CAUTION ONLY. THIS TIME IT WAS INCIDENT FREE AND WE HAD STOPPED WITH AT LEAST 4000 FT REMAINING. WE KNEW THAT THE DOOR WAS DIFFICULT TO CLOSE SO WE CHOSE TO STOP. THEN BECAUSE OF RECENT FAA ACTIONS; AS RELATED TO ABORTS; I STARTED SECOND GUESSING MYSELF. WHAT DID OUR OPS MANUAL SAY? WHAT DID TRAINING SECTION SAY; WHAT DID THE COMPANY SAY? MY FINAL ANALYSIS! IT REALLY DOESN'T MATTER WHAT THEIR OPINIONS WERE. WE HAD BEEN THERE; WE MADE THE BEST JUDGEMENT DECISION BASED ON THE CIRCUMSTANCES WE HAD BEEN GIVEN. I WAS THE FINAL AUTHORITY AND MADE MY BEST CALL.