Joseph Osse loaded his black sedan with a few guns, a steel target and a recording stand for his phone before driving into the desert west of Salt Lake City on a cold day in mid-November.

Mr. Osse, 32, began filming himself target shooting around a year ago for short videos he posted on YouTube. He has made over 300, with offbeat titles like “Plinking Steel,” “Art of the Mag Dump” and “First Person Rifle Cam,” that draw several hundred to several thousand views each.

Firearms content on YouTube has long been relatively niche, an algorithmic recommendation that can appear after viewers watch a Call of Duty video-game stream or search for information about the slick guns used by John Wick, the popular movie hit man.

Mr. Osse, who posts under the name Graizen Brann, learned how to shoot by watching the YouTube channels he is now trying to emulate. In the past, firearms education was often bestowed by older family members, and picked up in youth groups or by joining the military.

“I enjoyed what I was doing,” he said. “And maybe if there was anyone else on the planet that felt pretty much the same way I did about firearms that they would go ahead and subscribe and just see what happens.”

A new generation of American gun owners who are younger, more racially diverse and drawn to tactical training and self-defense are regularly watching firearms channels. The content has garnered more than 29 billion views on YouTube, according to unpublished data from researchers at the Institute for Strategic Dialogue and the Atlantic Council’s Digital Forensic Research Lab. It has made for a growing subculture commonly referred to as guntube, with creators known as guntubers.