We have dealt with patented products of our own. I find it hard to think of something that fundamentally changes the "art" of a magazine that would be allowed as a patent.
One way to look for such a problem is to examine the magazine. Generally there has to me marking on a patented product indicating it is protected under a patent, and anyone clever enough to patent an idea usually advertises it very clearly.
Trademarks and copyrights are much more common and all you need to do is figure out, for example, an unusual name for something. You can trademark the name so no one else can use it. Presenting yourself in the market as Ruger Arms with their logo would be an infringement. "Henry Ruger Slicker Than Snot Magazine" company would be unlikely to be termed an infringement, if you see where I am going.
Rumor is Ruger copied a Kel-Tec design for their little .380 auto. I dunno either way, but it does happen, and I haven't heard that Kel-Tech went after them.
Loyalty to petrified opinions never yet broke a chain or freed a human soul in this world — and never will.
— Mark Twain