You're right, partially because everyone who didn't give up their gun(s), and I would be one of them, automatically became criminals by so doing.
If you had refused to give up your gun(s), you would have got a prison sentence. A lot of sports shooters sent their pistols abroad, so they could use them on holiday.
The number of crimes that are committed with a firearm have increased even though virtually all handguns were prohibited in 1996. Also a larger proportion of violent criminals are armed compared to pre-prohibition.