Damage Question regarding charged rounds and the buff hammer and the Heavy Flak

[Moriarty]

Ok so unless i messed up (entirely possible) it takes 5 shots to kill a practice dummy with charged rounds from a heavy flak.

It also takes 5 rounds to kill it when you buff normal rounds.

This is understandable as the buffs are +25% and +30% respectively.

However what i don't understand is also takes 5 rounds for a buffed heavy flak firing charged rounds to kill the practice dummy.

Only thing i can think of is that either there is no stack, OR.

The lack of overflow from armour damage to hull damage (i think that's how it works) means that most of the damage from one of the shots is wasted.

I have a feeling the second one is correct. Its just weird that the practical effects of a +55% damage buff are rendered unnoticeable. 

[Queso]

It makes much more of a difference when multiple weapons are in effect such as a piercing weapon. A single weapon against a single ship shouldn't be balanced the same way as a whole game.