ON A MISTY November morning just after sunrise, I pulled up to a shooting range in central Texas with a borrowed AR-15 and a few hundred rounds of dubious-quality Russian ammunition that I’d ordered over the internet. I followed a pickup down a gravel road and over two cattle guards to the far end of the property. Then I parked in a field ringed by trees whose bark was scarred by stray bullets. A handful of men had already arrived, and they were loading ammunition into their magazines as the morning birds chittered overhead. After a while, a decorated US Army veteran named Eric Dorenbush gathered us into a circle and gave a short safety briefing—don’t point your barrel at anything you’re not willing to destroy, act as if every gun is loaded—then he asked us not to share any images or videos on social media. We didn’t want information falling into the hands of terrorists or other bad actors, he explained. Plus there could be social repercussions. “This activity is considered … off-mainstream,” one of my fellow students, an orthopedist from Indiana, told me. We had all signed up for a two-day tactical firearms course, where we’d be learning how to shoot as if we were engaged in small-unit armed combat. Once the purview of law enforcement officers and military operators, these kinds of skills are increasingly being passed down to ordinary, armed Americans by a sprawling and diffuse industry. Gun ranges and private facilities around the country teach the art of tactical shooting, in setups that range from the fly-by-night to the elaborate: At a Texas resort, you can schedule a combat training scenario inspired by the Iraq War after your trail ride; at an invitation-only facility in Florida, you can practice taking down a mass shooter at the Liberal Tears Café; at Real World Tactical, a former Marine will teach you how to survive “urban chaos through armed tactical solutions.”