I have not *ever* purchased a firearm in the state of New Jersey that came with more than a 10 round magazine in the box with the firearm. Manufacturers package firearms with different features and accessories depending on state laws. New Jersey's 15 round limit was unique among the states for years so many firearms were sold with 10 round magazines instead of, say, 17 round magazines sold in free states. That's not to say that thousands of pistols weren't sold here with 11-15 round magazines but I have never purchased one and I don't think it adds up to a million owners. And why turn it in when you can sell it out of state, store it out of state or in the case of a magazine that is of little value, just take the spring and follower out, stomp on it and throw it in the trash?
So I kinda doubt it.
New Jersey is a small state. Almost everyone has a friend across the river in the Free State of Pennsylvania to hold onto magazines as this winds its way through the courts. California is in the lead through the courts now, New Jersey is following at the tail-end.
Something very important in what you say here...
“California is in the lead through the courts now, New Jersey is following at the tail-end.”
And opposition to these actions need to be directly funded in mass from everywhere to nip them in the bud before they spread to other states who will take advantage of the precedent and follow suit.
But as far as details concerning magazine laws it is important to keep a close eye on the wording. This was the issue with the recently proposed magazine regulation in Florida. It was worded that any “firearm” with a capacity of more than ten rounds would be illegal. (not “Magazines”)
So this means even a 10 round magazine would still be illegal because the “firearm” it’s self will actually hold 11 total with one in the chamber. How these laws are worded is super important.
15 round magazines were still very common with pistol purchases around 20 or more years ago, even with the 15 round limit. I saw plenty on display in cases at local gun shops. So there’s still quite a few out there, sitting in people’s homes. And there’s likely plenty of owners who aren’t even aware of the new law.