So I'm playing around with the idea of writing a novel. I'd like the novel to be mostly realistic or plausible, and in the climax of the novel I'd like my protagonist to fire a railgun. However unlike in my picture, I'd like a human to be capable of carrying it. So my question is
>is the power of a railgun a factor of the barrel length (# of coils) or the power supplied (in my theoretical case a huge as bank of Capacitors)