it depends what you use if you use normal explosives like c-4 and tnt its pretty hard. but if you use super explosives like dest or bomb its extremely easy.
my bomb destroys all of it
i got super nuke (and completly destroyed 1,2 and 3, olmost 4)
in all honesty its not terribly hard
i have a weak bomb, and i have a super nuke (2 different bombs)