Here are the number of homicides by guns in the US (by year)
In 2023, 13,529 recorded murders in the United States were committed by firearm.
www.statista.com
From 2006-2019 there were an average of 9526 gun homicides per year. About 30% of those, 2858, are committed with legal firearms. Only 3%, or 286, of all gun homicides are committed using a rifle (or what the anti-gun lobby likes to deem assault weapon). So even if they confiscated all AR-15 style rifles tomorrow it would have a negligible effect on gun homicides in the United States.