Could you imagine what this would do to the economy. It would be like wiping out an entire industry. Relate the gun industry to the car industry but on a smaller scale.
You basically have your raw materials, manufacturerers, sellers/suppliers, and aftermarket.
Everyone who's involved with the raw materials and manufacturing would suffer huge losses, layoffs, possible bankruptcies of entire companies do to large overhead (unused buildings and equiptment) vs. minimal sales. Don't forget we would also be talking about ammunition manufacturers.
Then you have your sellers and suppliers. A gun shop can not afford to stay in business by selling O/U and single shot shotguns, and bolt action .22's. This would both affect retail giants as well as kill the mom and pops out there.
Aftermarket. Who needs a gun safe with no guns to put it in. No need to make more magazines if they're illegal. Think of all the little odds and ends you see on the shelf that if they were gone, the whole company wouldn't even exist.
Between the manufacturing/sales/suppliers/aftermarket you are talking 100's of millions of dollars if not near or over a billion per year in revenue. When that revenue isn't being redistributed through salaries, employment and so forth you're in a world of hurt.
I would liken it to a ban on fishing, or a ban on golf. When you ban the poles and you ban the golf clubs just think about how many people lose their jobs due to this chain reaction. It would take many years, but I think the effects on the economy would be somewhat significant. It would also effect all of the foreign companies greatly as well. I imagine that America is probably their number one consumer or buys a large percentage of weapons sold.