Short Barrel Tradeoff

Lately I've been hearing how short, concealable weapons are so "deadly," in the news. But in reality, there is a tradeoff for concealability, and that is bullet energy---also called lethality. And the tradeoffs are dramatic.
In this video JJ used the same ammunition (.223 and 9mm) in several guns of various barrel length to record the drop-off in velocity and energy. The results are eye-opening, and something that hunters have known for eons.