The pro gun control position is fascinating. Even ignoring the constitutional issues... How do you deal with the fact the horse left the barn a long time ago?

The pro gun control position is fascinating. Even ignoring the constitutional issues... How do you deal with the fact the horse left the barn a long time ago? Squinting at online sources, there's around 270M firearms in the USA today, is the plan to kick down doors and gather all those? Proof of concepts for 3D printed weapons already exist, should printers be controlled too? Machine shops? Does the southern border need to be locked down to prevent the emergence of future smuggling routes? Also, given that so many leftists believe Trump is a Hitler redux, is disarming the public really wise?