I'm not a deep-in-the-weeds expert, but if I had to put together an "obvious long rifle mistakes in fiction" article, it’d probably be:

* People pumping shotguns after every round, or unnecessarily cycling the bolt after every round

* Wrong action type for the gun

* Wrong shotgun ammo for the context

* Wrong safety type for the gun (most long guns have safeties, but they are operated in a variety of ways)

* Magazine vs clip vs chamber vs tube

* Shotgun impacts launching people across rooms, or unrealistic recoil (both too high and too low) for the weapon type