To take part, gun owners will register their firearms online. Once registered they turn the firearms in and then wait and hope to be paid.
The problem is once you register your firearm you're obligated to turn it in. You. may get fair value for it, $300 for it, or the pot of money runs out and you get fuck all.
That money is going to go fast. There's around 95,000 AR15s registered in Canada. At $1800 a pop that's $171 million out of $700m
There's a hell of a lot more now-illegal long rifles out there. I've seen estimates at a 1:10 to 1:20 ratio of Ar15 vs other banned semi-autos.