Question on CannonDragon Bal-Gunner

its effect states that when it brave attacks by drawing a card destroy one of your opponents spirits with 4000BP or less. so if my opponent doesnt have a spirit with 4000BP or less can i still activate this braves effect to draw a card.

Hmm... well, since our wording is unofficial, I can't say if you have to destroy first before drawing or you can draw and not destroy. However, I'm more likely to go with the first one, it just sounds more...balanced, somehow.

It should be:
Draw a Card, then destroy a spirit with BP4000 or below.

you still can get a draw because player gotta do what it says first...(In japanese i play)

the destruction effect still working, just there is nothing to destroy...Xd get it?

Like the Deadly Balance says "BOTH" didn't say like "destroy first...then destroy opponent...". you can still activate it even you are empty field.

Some sort of skill: Magic with flash timing effect still can be used for nothing but wasting your core for purpose of killing by depleting your spirit's core to avoid the effect of opponent's spirits says "when battling kill opponent's spirits...".