Establish a $250 tax rebate/credit available to all citizens filing tax returns, payable to those who turn in functioning handguns to be destroyed.
Along with the rebate/credit, create a framework for receiving handguns, verifying their destruction, and reporting back to the IRS that credit is due. Local law enforcement and volunteer organizations in each state can manage the process once the framework is in place.
While the focus right now on "assault weapons", such weapons account for a tiny percentage of gun violence. The real problem with gun violence is the huge volume of cheap, readily available handguns. This program provides financial incentive to turn in handguns, and creates a floor price in the market, helping prevent the ongoing sale of cheap handguns in secondary markets