As I understand the question, its about literature (books) where the author identifies the guns being used specifically. Not about whether the author get it right, or whether the work is a paragon of literary value or complete trash...
Ian Fleming's Bond series is iconic for identifying certain guns, and legendary (in the gun community, at least) for not getting things quite "right"....
Some authors take the approach of what might a real character use, and be able to do with it. Others don't. That may be ignorance on their part, or they might claim literary license.
One (bad) author of action novels (don't recall the name anymore) knew all right names for things but when he used them, it was like he just put them all in a hat and picked a "gun term" when he needed one.
I found the Executioner series back in the early 70s, when I was still riding my bicycle 11 miles to get to a bookstore. And I freely admit what attracted me at first was the Auto Mag on the cover. Soon after I began reading them I realized that while the author knew names and data, he didn't know real shooting, or Mack Bolan was superhuman.
A 600yd shot, from a boat on lake Michigan, with a .460 Weatherby with a 20x scope ("riding out the recoil" so he never loses sight of the target) taking a golf ball off the tee as the mob boss makes his backswing? Really?
Well, it is
fiction...after all...