NON TWR ARPT REPORTER ADVISED ON UNICOM WOULD BE DEPARTING BEFORE LNDG ACFT WOULD BE ON FINAL. LNDG ACFT MADE SHORT APCH RESULTING IN A GO AROUND.

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I WAS #1 FOR TKOF AT RWY 32 AT BOIRE ARPT IN NASHUA; NH. AN SMA X RPTED ENTERING LEFT BASE FOR A LNDG ON RWY 32. I ADDRESSED THE SMA X ON THE UNICOM FREQ AND ADVISED THAT I WOULD TAKE THE ACTIVE FOR TKOF BEFORE HE TURNED TO HIS FINAL LEG. THE SMA X PLT THEN CUT THE CORNER AND TURNED TOWARD THE RWY ON A MODIFIED BASE/FINAL OR CIRCULAR PATTERN AND HE ADVISED OVER THE RADIO THAT HE WOULDN'T ADVISE IT BECAUSE HE WAS GOING TO 'CUT IT CLOSE.' AS I WAS ALREADY ON THE RWY; I BEGAN MY TKOF RUN AND EXECUTED THE TKOF AND LEFT THE AREA. THE SMA X EXECUTED A GO AROUND. THE PREMATURE TURN TO FINAL BY THE SMA X WAS A CLEAR ATTEMPT TO ESTABLISH A RIGHT OF WAY IN FAVOR OF THAT PLT. HAD HE EXECUTED A RECTANGULAR PATTERN; THERE WOULD HAVE BEEN AMPLE TIME TO EXECUTE A SAFE TKOF W/O ANY CONFLICT. I WOULD SUGGEST MORE EDUCATION AND ENFORCEMENT IN THE AREA OF EXECUTING RECTANGULAR TFC PATTERNS AT UNCTLED ARPTS. I HAVE OBSERVED SEVERAL OTHER TFC CONFLICTS BTWN UNCTLED ARPT REGULARS WHO TEND TO FLY VERY CLOSE; NON RECTANGULAR PATTERNS; AND PLT UNFAMILIAR WITH THE ARPT WHO TEND TO FLY BY THE BOOK OWING TO LESS FAMILIARITY WITH THE TERRAIN.