This discussion is getting a bit confusing for me non-native english speaker, so bear with me when I try to sum it all up a bit:
All damage values in AH2 are given in lbs "bomb-equivalents."
Now when comparing different weapon systems (torpedoes, rockets, bombs, shells) keep in mind that the actual percentage of explosive fillings varies substantially between different weapons. Bombs have a much larger part of their total mass as explosive charge than cannon projectiles.
A hangar in AHII needs 2781 lbs of bombs to be destroyed. That roughly translates into 1390lbs of actual explosives.
The same hangar can be killed by 18x 5"HVAR rockets, which gives each rocket a destructive power of ~156lbs "bomb-equivalents", which would indicate a explosive load of about 78lbs for a single rocket. Actual warhead weight of a 5" HVAR rocket was 55lbs TNT
But when shooting 75/76mm HE tank shells at it, you also need 18 shots to bring a hangar down, thus giving them also a "bomb-equivalent" of 156lbs. But actual explosive filling of a 76mm HE shell (Soviet 76.2-mm OF354) is only about 1.4lbs, not 78lbs!
This little example shows that cannon shells are way overpowered vs. structures when compared to bombs. (Though it mays have been made that way for gameplay reasons)
