As reporters at The Wall Street Journal, Zusha Elinson and Cameron McWhirter have covered more mass shootings than anyone would care to recall: San Bernardino, Sutherland Springs, Las Vegas, Orlando.

But when they set out to write an article about the business behind the AR-15 — the gun often associated with this most American of tragedies — they found that its story was more revealing of the country’s recent history than they had imagined.

“It’s almost like a Zelig of guns,” McWhirter said. “It keeps popping up, from the 1950s of its invention until Jan. 6, when they’re waving flags that say, ‘Come and take it,’ with an image of the AR-15 on them.”

Elinson and McWhirter’s reporting evolved over the course of years into a deep dive into the personalities and circumstances that took the AR-15 from an idea literally sketched on the back of a napkin to one of the most powerful symbols of America’s contemporary political divide.

The resulting book, “American Gun: The True Story of the AR-15,” centers on the life of Eugene Stoner, the weapon’s inventor. The book traces the story of Stoner’s creation alongside a disparate cast of characters, from John Wayne, who by happenstance was the first civilian to fire the gun, to Cold War figures strategists like Curtis LeMay, to the many people whose lives have been altered irreversibly by the gun’s destructive force.

Elinson and McWhirter spoke about their research and the role they hope their book will play in the national conversation on gun violence. This interview has been edited for concision and clarity.

How did you come to this story?

McWhirter: Once you start to study this rifle, this fascinating story unravels about its inventor, this guy who was really an unknown, tinkering in his garage in Los Angeles, yet was somehow able to think in a new way about firearms. As soon as he created the AR-15, he lost control of it. That’s the story that we wanted to explain: How do you get from a guy tinkering in his garage, a former marine trying to invent a rifle to help American soldiers and their allies during the Cold War, to children running for their lives in a school shooting.

Did your research take you in directions you didn’t expect?

Elinson: When you think of America as an ideal, this story is what’s promised to us: A guy has an idea; he believes he can change the world. He has no college education, no training in gun design, but with his ingenuity he comes up with this very futuristic (at the time), lightweight rifle that the military ends up adopting. So from the beginning, it’s a very American story.

One of the things that we’re really proud of is that we’re telling Stoner’s story for the first time. There’s been a lot written about him and a lot of people think they know about him, but we were really fortunate to earn the trust of his family and talk with them over months and years to better understand who this guy was. They also provided us with documents showing his thoughts about the gun. One of the key things we try to answer in this book is: What would Stoner think about what’s going on today?

Why is it that the AR-15 became this symbol, and not some other gun?

McWhirter: There are a lot of events that played into this gun becoming the country’s most popular rifle, but certainly one of those is Stoner’s focus on using new materials that made it very easy to shoot, and very easy for a soldier to shoot rapidly and carry lots of ammunition with him into the field. Those design elements are having a big impact today.

Elinson: Politics was a huge factor as well. Going back to the 1994 assault weapons ban, the AR-15 was kind of an afterthought at the time. But once it was included in the ban, many of the people who owned the gun suddenly started to see it as much more than a gun. We talked to people who owned AR-15s at the time and they said, “This is the line in the sand. I know they aren’t going to touch my handgun; I know they aren’t going to take away my hunting rifle.” So suddenly, the AR-15 became the embodiment of the fight over the Second Amendment.

Do you expect people on different sides of the gun debate to read this book differently?

McWhirter: We don’t want anyone to walk away from our book saying this is pro-gun or anti-gun, or pro-AR-15 or anti-AR-15. This is an amazing object that has changed our world and we need to understand it. But we’re anti-mass shooting. We want people to know this history so that all Americans think about how we solve the problem we’re facing.

How are you hoping that the book contributes to that conversation?

Elinson: Unfortunately, a lot of our culture’s opinions and views of firearms are framed by very partisan lenses. What we wanted to do was lay out the history as objectively as possible. But we also wanted to show what it’s like for people who survive these mass shootings to live with the injuries. A lot of times, after the news vans leave, people forget. We really wanted to show the impact on their lives.

McWhirter: It’s become this object that we’re all fighting about, and yet there’s such little understanding of how it was created and how it became the American gun.