Removing 7-8 tons(approx 70 seats and pax) of payload only just makes full fuel viable in most cases for the A300. On full tanks, landing with normal reserves, would give the a/c 7-8 hrs flt time. So you can forget long haul in this config, it would still struggle to get back from Bahrain. Fuel tank capacity is the real prevention to long haul for this a/c!