Responsible gun owners have a duty to keep guns out of the hands of criminals. If you are forced to surrender your guns against your will make sure they are useless. Just in case they get lost on their way to be destroyed. For safety.
A dab of JB weld in the chamber should do the trick. Once the bolt closes, it ain't ever shooting again.
EDIT: To all the folks saying "Muh 1776!"... Only a small percentage of Americans went to war with the redcoats. A lot of people comply, for many reasons. This is for them, retailers especially, they can at least guarantee these guns don't go to Ukraine, Syria, ISIS, Gangbangers, etc.
Well over 90% of mass shootings are in so-called "gun free zones," where the shooter understands there would be essentially zero chance of being opposed by anyone with a gun. He has a free ride and he can take his time. Reloading is no problem, so magazine capacity limits have no utility. I have taken to calling these zones "shooting galleries," because of this fact.