If you watch the boarding scene in Master and Commander, a guy unloads a Nock's into a crowd of French sailors...it was IMPRESSIVE to see it go off!
The Rifle Shoppe carries parts sets for this beast, but I think that the barrels alone go for over $200.00 a piece...that's around $1500 worth of tubing, if anyone is keeping count.
When I first saw the Nock's, i thought that it was a rotating affair, like a pepperbox...when I found out that they all went off basically at once, I cringed all over. I read a report once online from the British Ordinance Department regarding the volley gun. In a nutshell it said that the soldiers who fired it refused to do it more than once and reported that the recoil was "stout".
I guess that's nice talk for "it pounded the living @#$% out of me"