In every election year, the two major parties raise money using the legislative process.
One party will introduce some bill, and then send out fundraising letters to their registered voters explaining how they're fighting for this-or-that cause, and if you do your part to keep them in office, you'll win. The other party will send out fundraising letters to their voters citing the same legislation, and warning that the sky is about to fall if that bill is passed, so please send them money to fight against it. It's how the game is played...
The last time Congress passed an Assault Weapons Ban, the House changed hands in the next mid-term election, and neither party has forgotten that. This bill is all for show, I think, and it isn't going anywhere. JMO...