As our friends behind enemy lines in CA recently found out.
The days of them going to the local store an easily picking up 500 to 1000 rounds for them and their friends to go on a weekend range trip just abruptly ended.
Same with the magazines, for the foreseeable future, they are stuck with whatever standard capacity magazines they had before the ban long ago or bought during the short court opened window. Those magazines may be the only standard capacity ones they will be able to legally buy & possess in their state for the rest of their lives.
Only if everyone rolls over, but so far that looks to be likely what would happen.