Got another idea here!

Name: C87-SE Assault shotgun
Manufacturer: Krome
Ammo type: 12 gauge shells
Clip size: 14 shells
Primary fire: Single fire
Secondary fire: Load extra shell into the main chamber
Special fire: Use stock
Firing modes: Pump-action, automatic fire

Short history:
The C87-SE may seem like a normal shotgun, but unlike other shotguns, it has 2 chambers: A Loading chamber, and a main chamber.
The shells are loaded into the main chamber from the loading chamber via a cilinder.
the main chamber can hold up to 4 shells, when fired, all the shells in the main will be firred all at once.
The stock can be folded out to reduce the recoil.
This weapon has gotten the nickname: "The Black Dead", because off it's enormous power.

if you had mulitple shells in 1 chamber and you fired it, the gun would explode. Why would you need a loading chamber when you got a magazine where all the rounds are stored anyway.

you got quitte a point there, a magazine would be indeed better than an extra chamber...

y not simply make the second chamber into another barrel?
and when you press special, it loads cocks a round into the spare chamber and use secondary fire to shoot both barrels at once.
and leave the stock deployed permanently
and make it a clip fed weapon..

That would be an interesting design. I wonder how the mechanism for that would work, in order for it to load that second chamber that phase of the process would have to be manual, once loaded it could then run auto after firing.

Actually, it could just grab the shell, spin it around into the other barrel, and then load a new shell into the main mechanism. After that, you just have an extra hammer to shoot off the second barrel. Other than that, both barrels would work like normal.

Spin? how would you do that? If your thinking of the way the p90 works then imagin the p90s mechanism UPPED big time to facilitate a 12 gauge shotshell, the p90 works well because the round it uses is very small. The same mechanism for a shotgun would be huge and if your thinkning of something like little fingers or a grabber flipping the shell that wouldnt work either because moving parts in most semi autos are driven either by the recoil or by the gas tapped off through a hole in the barrel and channeled to a bolt carrier of some sort which cycles the weapon, this all happens very quick and the parts cant be thin pieces of metal they have to be strong pieces and somewhat simple because of the force and pressures built up.

You also wouldnt need 2 hammers if you want the rounds to fire off at once, just put 2 firing pins into the same boltjust make a wide bolt that can lock both rounds into both barrels and just give it a hammer that is kinda like a T that way when the trigger is pulled both rounds go off exactly at the same time.

Sorry for the long post i think im over analysing the situation.

Well, I'm thinking about the spinning part in a different way probably from you. My spinning though is where it has a hook that spins forwards rapidly and shoves the shell into the other barrel around a small arc for the shell to travel through, and then the hammer mechanism can fire on it. Of course, the hook mechanism can only return after the shells are fired, and then it needs to move back in place before the next shell gets loaded.