[TheWanderingMind]

I believe what the gent was speaking of is called a "volley gun." It was a naval/marine flintlock weapon used for boarding enemy vessels back in the wayback... I've seen a museum example of the weapon, there's one for sale in England right now, (www.johnsloughoflondon.co.uk/AntSite/thumb/50.jpg) and it's a 7-barrel from 1779.

Doesn't nobody read swashbucklers anymore?

[Wingwiper]

Sooner

Actually during the American Revolutionary War, a fellow invented a Automatic Muzzle loader. Yup! you heard me correctly.
It had a single barrel, but it had a forward and rear Touch hole, each ball had a small hole drilled through it and there was powder, ball, powder, ball for 5 times in the rear, seperated by a cloth patch and then powder, ball, powder, ball etc in the front of the forward touch hole. The Hole of the ball had powder in it and it worked this way. If you wanted to fire FIVE shots, you ignited the forward touch hole and five balls would go off and then stop. When you wanted five more shots to go off, you ignited the rear touch hole. To reload, you replaced the barrel with a pre loaded one.
Congress paid for the developemnt of this firearm but never accepted it and ended up paying the creator I think $10,000 per year for the rest of his life.

During the Civil War there was indeed a multi barrel rifle that worked like the Gatlin gun, somewhat.