We know that there are an estimated 300 million guns in America. I wonder if that is "legally" owned plus "illegally owned" or just "legally" owned. How many guns are in the hands of criminals today, or people who have no compunction about delivering a gun to a known criminal for a profit? Those guns will never undergo a change of possession WITH an associated background check. Neither will the guns which are stolen from people who legally own guns. Once the guns are stolen, they exit the government registration scheme. This will not reduce crime. It's going to get expensive and it will deliver little, if any, benefits.
"If you love wealth better than liberty, the tranquility of servitude better than the animating contest of freedom, go home from us in peace. We ask not your counsels or arms. Crouch down and lick the hands which feed you. May your chains set lightly upon you and may posterity forget that ye were our countrymen." Samuel Adams.