There was an attempt; it did not work.
On January 24, 2013, Dianne Feinstein and 24 Democratic cosponsors introduced S. 150, the Assault Weapons Ban of 2013, into the U.S. Senate.[19][20] The bill was similar to the 1994 federal ban, but differed in that it used a one-feature test for a firearm to qualify as an assault weapon rather than the two-feature test of the 1994 ban.[21] Such a move would deter the average gun owner from wanting to purchase a neutered rifle.[22] In addition, it banned:
the sale, transfer, importation or manufacture of about 150 named firearms; firearms with thumbhole stocks and bullet buttons; the importation of assault weapons and large-capacity magazines; and high-capacity ammunition magazines (defined as those capable of holding more than 10 rounds).[21]
It would grandfather in weapons legally owned on the day of enactment and exempt more than 2,000 specific firearms "used for hunting or sporting purposes."[21]
https://en.wikipedia.org/wiki/Assault_Weapons_Ban_of_2013
After a specific date, you can no longer buy a broad category of guns, and if you have one, you can not transfer it to anybody except the government. It's confiscation by attrition over the course of most of a century as owners of granfathered guns die off.
That's the Democratic plan to address mass shootings: expand the definition of "assault weapon", then spend 80 years confiscating them. And this is the signature gun-control effort by the DNC.
I would have some respect for them if they simply said "all semi-automatic rifles are banned, no exceptions". What they're doing is useless pandering that puts republicans in charge.