Well the first Vikings were spyders with Hyper Frames. The new WAY BETTER (IMO) desigen is basically an open bolt Excal. It works similar to a bushy, imp, timmey, but with a really low pressure ram to push the bolt forward and open the valve.
They have just come out and are selling for 775 (milled) I believe. THere are a few places that sell AKA markers, You can get them factory direct and I think Paintballistics will be selling Viks too.
Correct me if I'm wrong anyone.