They tried the whole "register everything" in Canuckistan, and even those nice, pliable, compliant Canucks had a less than 10% compliance rate, and the whole scheme slowly faded away.
No telling how many pieces of 6" PVC pipe are buried around Australia, with certain contents, that nobody talks about. But I was told it was hard to get 6'" caps around the time of the great turn them in events.
Heck, 30 years ago I was working for a farmer in Holland in the potato harvest, and ran across what I now think was a Schmeizer, with a case of ammo, tucked into the corner of a barn. It had been "get your arse thrown in jail" illegal for dang near forty years by then, and the guy I worked for wasn't even born yet during the War.
Confiscation is not that simple, and simple non-compliance is a good place to start.
