From what I have read elsewhere there are over 200 million high cap magazines floating around in the US.
Such limits will never work.
That's a neat trick. Mine sank (unfortunate canoe accident).
The objective is to have something serious to charge you with so they can take your right to bear arms away.
Such limits are never intended to "work".
They are just another tool to use for harassing and persecuting gun owners. Particularly middle-class and otherwise law-abiding gun owners. Government officials really do not want ordinary citizens to have firearms for any reason at all. The peasants might actually refuse orders from a government official for some reason or other.
They do not have enough minions to enforce their orders consistently, so they must be very selective in their efforts. Make yourself conspicuous and they will come after you with an over-the-top show of force and maximum publicity. Terror tactics is how they roll.
High-ranking Democrats and members of the violent criminal underclass will be effectively exempted from such rules, and any relevant charges will be dropped. This is what already happens today under current restrictions. Expect more of the same.
That and the fact that anyone who can bend tin and attach a spring can make one, it’s not exactly magic..