Make it harder to get and drive the price up.
That way people who want to legally buy ammunition are prevented from doing so.
It is the same reason that Fast and Furious had the purpose of being an intentionally botched operation to help promote gun control legislation.
Obama, Hillary, Holder, and friends are out to take your guns!
Meanwhile, criminal types will be allowed to illegally own guns that they have stolen or used in crimes.
Hey, this opens up all kinds of possibilities for the tyrants. They want to get around the First Amendment - buy up all the ink and paper, silicon chips and TV time. Illegal searches and seizures? No problem - just call it a “Lockdown”. Some old parchment doesn’t need to get in the way of Fundamental Transformation anymore.