Yesterday's hunting rifle is today's "assault weapon", "sniper rifle", "tactical rifle" or whatever they decide to call it. Particularly with the term "assault weapon", they made up a new term, gave it a definition that had nothing to do with making the gun functionally different. Having a pistol grip, an adjustible stock, a mount that can accept any accessory as long as it can also accept a bayonet or grenade launcher (which are made to attach to a variety of mounts), etc, doesn't make the gun function differently. After the Aurora and Newtown shootings, they've now started pointing out "loopholes" in the law that allow people to still have "assault weapons" as long as the "assault weapon" doesn't have any of the evil features. In their eyes, any semi-automatic rifle is now an assault weapon, and they've started to mention pump action shotguns. They're redefining the term "assault weapon" to give it a broader and broader definition until eventually it will encompass everything more powerful than a RedRider BB gun.
They're not trying to blur the line. In their eyes, there is no line between hunting rifles and "assault weapons". They're just going to keep expanding the definition until they get everything.