You can start off firing 7.62x25, but by the time the casings hit the floor, they'll be .223. Check out the Matrix lobby shoot out scene for that one.
Neo was using his power as "The One" to do that. No, really.
...you are all getting sleepy... it was not a continuity error... return to your normal lives... forget... forget...
Anything that is too large to go up a nostril may be used as concealment in movies/TV.
Anything that in reality would provide concealment = cover in movies/TV.
Cover = invulnerability to any attack short of anti-tank rockets.
Most revolvers have safeties.
You can "fan" a double-action revolver.
Semiautos without external hammers may still be cocked(the police w/ Glocks vs. Trinity scene from the start of The Matrix).
Bad guy explosives cause smoke and sartorial damage such as shredded clothing(think of cartoon explosives).
Good guy explosives nuke whatever/whoever the Hero wants to destroy and leave everything/everyone else in the vicinity unharmed.
You can fight in a prolonged gun battle with lots of explosions without bothering to use hearing protection, and still hear a normal conversation(or a Bad Guy sneaking up behind you) immediately afterward.
Shooting a vehicle almost anywhere will make it catch fire and/or blow up.
Women must wear tight revealing clothing and impractical shoes that interfere with running, fighting, tunnel-crawling, climbing, or other athletics. This rule applies even if they know ahead of time that such activities are likely. No matter how durable the clothing is, it must get torn in such a way as to make it more revealing.
A Hero who takes his shirt off becomes harder to hit.
Rural people are inbred, gun-totin', beer-drinkin', 'baccer-chewin' gap-toothed rednecks who are just itchin' ta kill sumthin'. They often want to capture or kill the Hero. This is usually because they were gullible enough to fall for the frame-up that has forced the Hero to go on the run.
Rural people are all expert marksmen, outdoorsmen, drivers, brawlers, and mechanics. Their simple honesty and decency may seem naive and unsophisticated to City Slickers. They may seem deficient in formal education to the uninitiated, but they have a great deal of Common Sense and Mountain Wisdom that can save the Hero's butt.
Rural LEO's are corrupt and/or dangerously clueless("Yer sayin' that six hikers have disappeared and 'get out in the name of Satan' was painted in blood on a rock near where they were last seen? Prob'ly just teenagers pullin' a prank.").
Rural LEO's are Honest Forthright Cops, and your last hope when the Corrupt Cops/Black Helicopters/Evil Conspirators/Feds Who Mean Well But Who Misinterpreted The Evidence/Men In Black are after you.
The Hero's 9mm can double as an anti-tank weapon.
The Villain's .44 magnum can occasionally cause minor flesh wounds.
Shotgun pellets spread a foot per two feet of travel, allowing entire rooms to be cleared with one shot.
Corollary: The Hero may use low-brass skeet shells, they will transform into magnum armor-piercing heat-seeking 100-pellet 00000 buckshot shells in his shotgun. They will shorten so that he may load three times as many as usual. They will change back when ejected so as not to reveal the secret.
Glock makes a ceramic gun that does not show up on a metal detector.
Suppressors only need to be about 3 inches long and an inch wide, and they can make any gun sound like a kitten's sneeze.
A rifle may be used like a quarterstaff and/or a two-handed sword for an entire fight scene and it will still safely, reliably, and accurately fire.
Laser sights allow anyone to achieve sniper-like accuracy.
Gas masks don't interfere with heavy exertion, vision, or shooting.
It is forbidden to use ranged weapons against the Bad Guy who is a demigod in hand-to-hand combat. This applies even if the populace still has guns, bows, slings, javelins, or rocks. It is also forbidden to swarm him under with superior numbers, or to combine the above tactics(e.g. all of the Downtrodden Villagers throw rocks and fishing nets, then follow up with farm implements).
Corollary: If the Bad Guy is an expert pistolero, it is forbidden to snipe from beyond his range or to ambush him.
If someone begins to behave bizarrely, it is forbidden to behave as though you have noticed. It is against The TV and Movie Rules to attempt to determine whether or not he has been possessed, mind-controlled, or replaced by a clone/robot/shapechanger. If you attempt to test anyway, you may not restrain OR DISARM the subject while doing so.
Any semi-automatic firearm may be quickly and easily altered with ordinary hand tools to reliably and safely fire full auto. Gunsmithing skills are not needed.
The hero's CCW's never print, and he has reciprocity in all jurisdictions.