Known as a symbol of freedom to its admirers and an assault weapon to its detractors, the AR-15 is one of the most controversial weapons in America. Lightweight and easily customizable AR-15-style weapons have skyrocketed in popularity in recent years taking center stage at gun ranges and shooting competitions across the country.

Chapters: Intro: 0:00–2:17 Chapter 1 America’s rifle: 2:18–5:30 Chapter 2 Gun ownership in America: 5:31–7:35 Chapter 3 Gun-makers: 7:36–9:51 Chapter 4 Gun ads: 9:52–11:55 Chapter 5 Mass shootings: 11:56–16:29

According to the most recent national figures, there are an estimated 393 million civilian-owned firearms in the U.S. And there are about 20 million AR-15-style weapons in the country. Firearm manufacturers have seen revenue surge taking in about $1 billion from the sale of AR-15-style weapons in the past decade.

But the weapons have also been involved in a number of mass shootings. AR-15-style weapons were used at shootings in an elementary school in Uvalde, Texas, a Fourth of July parade in suburban Chicago and a grocery store in upstate New York. Critics argue the weapons are also aggressively marketed by gun companies targeting at-risk young males.

So what is behind the popularity of the AR-15 and what responsibility do gun makers have when their products are used in mass shootings? Watch the video to learn more.