sure, but i guess what i mean is like, that's why the meaning of the idiom is clear to me even having not tested or watched someone test what the actual effect of firing a gun into a barrel full of fish would be. if you were ever in a conversation, prior to watching that episode, wherein someone used the idiom to describe a task, and you were like "oh, you mean that'll be easy, because the shockwave from a gun shot would kill all of the fish in a barrel at the same time", before you watched the mythbusters episode, i guess you're a lot smarter than me