I know a guy who is a big wheel in a large gun club near Dallas. He gets calls now and then from people who say someone died and left some ammo behind and could he dispose of it?

So he does and a lot of it gets passed on to Police departments for training or disposal.

He has never received anything rare but he did get a Mauser rifle that was used in some South American country that was chambered in some weird round that only they used. So he can look at it but never fire it since ammo for it no longer exists.

Sometimes the difference between a rare collectors item and garbage is in the eyes of the beholder.