I suppose it depends on how you define “successful”. From New York Daily News:
The National Summit on Illegal Guns will take place next Tuesday. The event will begin with a symposium outlining successful gun control policies from cities across the country.
If they mean using legal restrictions on weapons to reduce crime then it will be a very short symposium. If they mean disarming the victims and enabling murder and other violent crime to increase then they could probably spend months on the topic. My prediction is they will measure success in terms of gun destroyed, not lives destroyed, by their illegal actions.