 In 1937 this firepower was enough to outgun the early marks of German Messerschmitt Bf 109, which were equipped with only four light machine guns.By the time of the Battle of Britain, however, it was recognised that this relatively small-calibre armament was inadequate; during the Battle of Britain it was relatively common for Luftwaffe aircraft to survive numerous hits from .303 in (7.7 mm) bullets and still return safely to base.Later versions of the Hurricane were equipped with a more powerful arms package, initially 12 .303 in (7.7 mm) Brownings, and later four 20 mm (.79 in) Hispano cannon.