My first impression was that this thing is a beast of a gun, and my second was that I could get a whole pile of S12s for the price.
The odd-looking structure on the bottom is not a pump. This is a semi-automatic shotgun fed by four feed tubes stuck together, and you rotate the whole magazine to the next tube once every four shots.
The one I saw had a breaching brake for added beastlyness and was stickered for $2,500. The shop owner said these things are selling like hot cakes and that he can't keep them in stock. Then again, the guy also claimed the SEALs had just ordered hundreds of