ACR CREW ELECTS TO DEPART WITHOUT TKOF PERFORMANCE NUMBERS FOR THE RWY LENGTH TO BE USED.

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TSTMS WERE MOVING INTO ATL FROM THE W. GND TAXIED US BTWN RWYS TO EXPEDITE OUR DEP AS WBOUNDS WERE SHUT DOWN. ASKED IF WE COULD DEPART FROM B2 ON RWY 8R; 9800 FT AVAILABLE. AS THE RWY IS 10000 FT I INDICATED YES. AT THIS POINT WE REQUESTED TKOF PERFORMANCE DATA; BUT AS WE TOOK THE ACTIVE NONE WAS AVAILABLE FOR AN INTXN TKOF. I ELECTED TO PROCEED WITH MAX PWR; ACCOMPANIED BY A HEADWIND; AS I FELT SAFETY WASN'T AN ISSUE. WE DEPARTED. HAD WE ELECTED TO GO FULL LENGTH; THE DELAY WOULD HAVE BEEN AT LEAST 20 MINS. HAD THE WX MOVED IN; IT WOULD HAVE BEEN LONGER. WE ALSO HAD INTL CONNECTIONS AT ORD. MY COPLT ALSO CONCURRED THAT; WHILE NOT OPERATING WITH A TKOF PERFORMANCE DATA FROM B2; 200 FT LESS THAN FULL LENGTH WAS NOT A SAFETY ISSUE. ANOTHER MINOR ISSUE WAS FUEL. HAD WE ELECTED TO STAY; LACK OF ADEQUATE ARR FUEL MAY HAVE CAUSED US TO GO BACK TO THE GATE. SUPPLEMENTAL INFO FROM ACN 471760: THE RWY LIMIT WAS 157400 LBS; OUR TKOF WT WAS 126500 LBS. 8 KTS OF HEADWIND WITH WX APCHING FROM THE W. IT WOULD BE AN HR BEFORE WE COULD GET OFF. MYSELF AND THE CAPT SAW NO PROB TAKING THIS; IN THE INTEREST OF SAFETY.