The Silence Of The Gun
The airplane is not an environment conductive to detailed exploration of deep issues, so I watched only (relatively) brainless action movies, where even if I missed some dialogues I could still enjoy stuff blowing up. You know, the A-Team, Predators, The Losers and that stuff.
Well, one thing I noticed in these movies is that everytime someone picks up or handles a firearm you can hear a string of clicking, clacking and clanking sounds, way beyond the classic (and acceptable, within limits) racking of the action.
I have some experience with handguns, rifles and shotguns and I can assure you that unless someone deliberately performs an act such as firing the gun, racking the action, flicking on or off the safety or inserting/removing the magazine the gun stays as silent as a piece of metal and wood or plastic can be. Simply picking it up or swinging it around does not produce a sound.
Moreover, of the above noises only a gunshot is truly loud; all the others would be easily drowned in even moderately noisy environments. I concede that in a moment of silence, some gun-related noises can bea heard rather clearly especially by a trained ear.
On the other end, I'm not sure it makes much sense to flick the safety on between one unexpected firefight and the other: too much risk of forgetting it and missing the chance to shoot. Even more inane would be to take a round off the chamber so that the action has to be racked again.
It is a matter of volume more than anything else, of gun-related sounds being amplified beyond their normal level for the show.