Doesn't sound like Joe Biden won them over, though that probably wasn't the point:
We were disappointed with how little this meeting had to do with keeping our children safe and how much it had to do with an agenda to attack the Second Amendment. While claiming that no policy proposals would be “prejudged,” this Task Force spent most of its time on proposed restrictions on lawful firearms owners—honest, taxpaying, hardworking Americans. It is unfortunate that this Administration continues to insist on pushing failed solutions to our nation's most pressing problems. We will not allow law-abiding gun owners to be blamed for the acts of criminals and madmen. Instead, we will now take our commitment and meaningful contributions to members of congress of both parties who are interested in having an honest conversation about what works—and what does not.
Anyway. One idea that's emerging from all the talk about possible gun control measures is that, if you have to pick one (as the politics may require), then a federal ban on large ammunition clips might actually be more effective than a reinstatement of the lapsed federal assault weapons ban.