Or are they actually after something else?
Their plan is to end all "civilian" firearm ownership. They may not get there, but they will certainly try and their plan is very simple. All they need to do is get a toe in the door by banning certain "highly dangerous" guns, aka assault weapons. Once they can subjectively ban guns, not a single gun is safe.
Additionally, they want to sue gun makers out of existence and tried that route before. Now that they feel the climate has changed, they hope to be able to go down that road again.
Banning guns based on looks, causing makers to shutter their doors, creating a gun owner database..... Yeah, that means they want more than back ground checks and magazine limits.
They want the guns that you are not "responsible" enough to own. Believe it.