The red line is when Republicans ended the national assault weapons ban.

Source:
https://www.channel4.com/news/factcheck/factcheck-does-gun-control-work
Also, https://www.instagram.com/p/CeEZJNJu5X2/
Note: In 2004 the Republican Congress refused to renew the assault weapons ban

FactCheck: does gun control work?

States with stricter gun laws have lower firearms deaths - but is one causing the other?

Channel 4 News
@AthenasOwl Also a timeline of Republican administrations. In Biden’s time the proportion has halved, but it was so much larger to begin with under Trump that it only has gotten down to where it expanded to in the past.