You don't need to confiscate all guns to practically eliminate gun crime. The UK didn't, we just adopted a harm reduction model, gradually controlling and then removing those weapons with the greatest risk for harm and the least legitimate use - handguns and semi-automatic centrefire rifles. It took decades, but it worked.
Start with a serious federal licensing and registration system. Establish a national database with comprehensive ownership records, including private transfers; require firearm manufacturers to submit forensic samples of bullets and casings for all new firearms. Mandate firing pin microstamping. Fix the known shortcomings of the background check system. Close the gun show loophole. Instate the five-day waiting period originally proposed in the Brady Act. Require secure storage of all firearms in an approved gunsafe. Introduce mandatory safety training. Impose considerably harsher punishments for reckless or dangerous use of a licensed firearm.
Once you've got all that in place, then you can start talking about buybacks, amnesties and outright bans, starting with Title II firearms. Mandate a legitimate sporting or professional justification for the purchase or transfer of any firearm. Ban large-capacity magazines, then centerfire handguns, then semi-automatic rimfire handguns, then semi-automatic rifles.
After 30 or 40 years of incremental progress, you end up with a society that has a negligible number of handguns and semi-automatic rifles, while still maintaining the rights of sportsmen and farmers to own shotguns and bolt-action rifles in a properly controlled manner.
You can do it, if you can muster a serious and well-funded opposition to the NRA.