From Guns.com:

Describing them as “concealable assault-style rifles,” a group of Democrats in Congress called on President Biden Wednesday to regulate semi-auto rifle-caliber pistols under the National Firearms Act. 

In a letter penned by Democrat U.S. Reps. Val B. Demings (FL-10), Joe Neguse (CO-02), Ed Perlmutter and Mike Thompson (CA-05), then signed by roughly half their caucus, contends that AR- and AK-style pistols should be covered under the NFA, a move that would require $200 tax stamps, registration, and layers of ATF red tape.