590lbs with guns, ammunition and oxygen equipment for the gunner, not a ton but heavy enough
The Defiant was intended to attack unescorted bomber formations and may well have been quite good at that. Nobody was expecting France to fall and for the Luftwaffe to acquire bases just across the Channel which it could use to escort its bombers with single engine fighters. That spelt disaster for the Defiant as a day fighter but it soldiered on and made the best of a very bad job as a night fighter and in some other roles.
A rather optimistic and factually inaccurate view of the type, and some nice film here.....
Cheers
Steve