First off, I'm not posting this in Politics and I hope it'll stay non-political. I want to think about the effects of a few of the most likely ban scenarios, not debate the likelihood of any of them.
That said, here are some of the facts at the moment. EBR's (esp AR's) had been becoming far more popular and accepted by the Fudd crowd for years. Everyone making a model, selling them in Walmart etc. With the recent ban talks, the internet sold out of everything: it's not as bad now but for over a week I literally couldn't find a single retailer who was not out of stock on any AK pattern rifle. I wasn't checking but I believe the same was more or less true of AR's. Any magazine over 10 rounds was basically sold out most places as well. Naturally prices skyrocket, doubling and tripling on rifles and going up even more on mags. I saw a 100 pack of pmags ($10 each the week before) sell for $7500. Ammo was pretty well cleaned out for the 5.56, 7.62x39 etc. So, a lot of new folks have EBR's, and a lot of folks who owned a couple before now own lots more. Many of them were bought at highly inflated prices.
Now, given that set of facts (and any others you care to present), what will the markets do in reaction to these scenarios?
1. DNC uses "compromise" on not pushing a ban or EO'ing anti-gun stuff to get the GOP to cave on fiscal cliff stuff. No change in gun laws.
2. No legislation gets through, but Obama EO expands the import ban. Not much changes for AR guys, but all the quality foreign ammo/rifles/mags dry up for the AK guys.
3. A mag capacity ban is passed, but nothing else.
4. A mag ban and import restrictions are put in place.
5. A more drastic ban is put in place, but one that is not so intolerable as to cause the frog to jump the pot.