First off, I think I agree with Stuart that the saying most likely refers to shooting a barrel full of dead fish... which would obviously be easy to hit a fish...
But, I understand why they'd test the live fish swimming in a barrel, since they couldn't verify the origins of the saying. The results though, seemed 'fishy'.
The shock wave from a 9mm doesn't seem like it's that big that it would kill fish in a barrel. I know they used their shock patches, and according to the shock patches that they would have killed fish.... but that just seems far fetched to my unscientific mind... I would have liked to see some goldfish in the barrel and shoot a 9mm in there and see what happens. I know that they would NEVER be allowed to do that, but that's what I wanted to see in order to prove or disprove their theory...
Grant and the jalapenos were pretty fun though.
And the grand finale barrel shooting was tons of fun, even if it was completely pointless to the myth itself.