The Omen was a stacked tube, closed-bolt, blow-back with an offset vertical feed and feed 'paddles'. It appears that everything started as someone asking "what if closed-bolt, but blowback?" Everything that followed was a series of interesting design choices chasing that dream. In order to allow the bolt to close after blowing back, the hammer is made of an inner and outer shell. The outer shell blows back, then returns forward leaving the inner hammer locked against the sear. To deal with the fact that blowback action is fairly violent, and the bolt would be returning at high speed, the feed was offset mounted with paddles that 'slap' the paint into the breech before the bolt slams forward.