Magazines by far. But there are gun rags and gun magazines. The older issues of Rifle, Handloader, Game County, Varmint hunter, The Accurate Rifle, Precision Shooter and others were often more technical journals than plain gun rags. Places were writers like Ken Waters, Ludwig Olsen, Finn Aagard, Gil Strung and others would write adult level articles on everything from the 7x33 sako to the processes of truing the bolt face and lugs on a '98 mauser to the historical background of the Krag-Jorgenson rifle before it was adopted as a US battlerifle.
I still have crates of these old magazines. Yes i still read them a lot. When I need information I can trust I revert back to these people, and the years of study that they offfered.
Rifle and Handloader were just released in there entirety on data DVD, If you really want solid information that is a place to start.