According to Official Guinness Records,
The heaviest bomber in service is the Russian Tupolev Tu-160 'Blackjack' bomber, which has a maximum take-off weight of 275 tonnes (606,270 lb) and a maximum speed of around Mach 2.05 at high altitude (2,511 km/h, or 1,560 mph).Its empty weight is 110 tonnes (242,500 lb). It is 54.1 m (177.5 ft) long with a wingspan of 55.7 m (182.7 ft). Although a Boeing 747 has a higher maximum takeoff weight of 397 tonnes (877,200 lb), the 'Blackjack' is considerably smaller and crucially, flies more than 2.5 times as fast.Maximum takeoff weight refers to its total weight when fully loaded with bombs, and in aircraft terms is an indication of the carrying capacity of the aircraft.
For a complete list of 1981 records, please visit 1981 Guinness Records in Russia.