New York passed the "safe" act after the Sandy Hook shooting, requiring existing "assault" rifles to be registered with the state. Not one person I know has registered their rifles, from friends with several to relatives barely into shooting. There was a FOIA request for the total number of rifles that got registered, NY state resisted releasing the number but eventually did. 50k rifles registered when it was estimated that there are 1 million rifles that qualify in state. 5% compliance. For registering. I'm sure you'd get similar numbers if there was ever a ban that required all firearms to be turned in.
Edit: Here's a Forbes article on this