Setting the Scene: Getting Guns Right
Knowing a little something about weapons can increase realism.
Sooner or later in your game, violence will ensue. Outside of the fantasy or historical setting, it's likely going to involve firearms. Having been a firearms enthusiast for over three decades, long before I even owned my first weapon, I found that knowing something about weapons lent a certain verisimilitude to our gaming. Here's a few common mistakes:
Revolvers don't have active safeties. Okay, this is not always the truth: some Manhurin revolvers and the Webley-Fosbury "automatic" revolver from the early 20th Century had one. Neither do Glocks, but most other polymer frame striker-fired handguns over a variant with a safety you can click on to stupid-proof your weapon. This might seem a small thing, but it can play into the storyline -- pistols with a safety on might buy or lose a character the initiative in a fight. But more to the point, when you're running a game — be it a military campaign or police procedural — for someone who knows their guns, they're going to notice stuff like this.
Next, semi-automatic and full automatic are not the same thing. The first means the weapon fires once per trigger squeeze -- just like a revolver; the latter means the weapon will continue to fire until you let off the trigger or it is out of ammunition. Autofire burns rounds fast. This is where the abstract ammo system in the Year Zero games from Free League gets it right. Did you panic? If you left your booger hook on the bang switch for too long, you’re out of bullet, Joe. You can empty a P90 with 50 rounds in the magazine in a matter of seconds. It’s actually stupid, which is why most militaries use a burst function on their firearms — to prevent soldiers from blasting through all the ammo needlessly. Depending on the weapon, it’s usually three rounds per pull, but H&K likes to have a single, 3-round, and 7-round burst function on some of their submachineguns.
Also, autofire is not magical. It's not like a grenade going off, killing everything the bore crosses. It's not particularly accurate, nor is it the opposite. Some game mechanics make it out that the accuracy going to hell, but damage going stratospheric. Not really true. For those who haven’t experienced it, full auto is pretty much useless; after the first few rounds, you’re shooting the sky. If you’ve shot full-auto, you’re not going to be on target past a few rounds, especially with old school .30-caliber battle rifles, but you’re not going to be firing willy-nilly. Full-auto isn’t really to shoot stuff. You use it to keep people's heads down and in one place until the other guys you're working with can get into position to take the target down. That method of "spray and pray", though, looks great on movie screens.
Called shots: most games make this incredibly hard, and when you're jumping around looking for cover while your opponent is doing the same...well, it is. But when the shooter has a few seconds to aim and take their time -- a shot to the hand out to 15 meters is a difficult, but not impossible shot. Hitting the head is usually not as difficult as game mechanics make it out to be through standard pistol ranges of contact to 20-25 meters; for rifles, a head shot out to 100 meters isn’t much work.
Here’s one that’s really annoying: “The character's not strong enough for this gun” nonsense. This is one of the most annoying tropes in RPGs -- strength limits to use a weapon without penalty. Most handguns and rifles are perfectly manageable, even for relatively weak folks. The worst are actually the really small revolvers and autos chambered for something moderate to heavy, as well as the big bore African hunting howitzers. The first hurts your hand and its unpleasant...but you won't notice in a gunfight. (You won't notice you peed yourself until after, also.) The heavier the gun, the more recoil will be mitigated. A 12 gauge shotgun can be fired one-handed with control, but if you don't seat it against your shoulder properly, it hurts (no...you won't break your shoulder.) A .458 Grand African, a .416 Rigby (I know a guy had his retina detached from the recoil), and the .500 Nitros are just plain unpleasant. And unless you're hunting a rhino, Cape buffalo, or elephant, they're simply unnecessary.
Bigger is better: Keep that in mind when your bad ass elf assassin in Shadowrun picks out her ordinance...she's probably wouldn’t hang a six pound Desert Eagle with scope or laser sights or other nonsense under her arm. It’s big and heavy and that’s really tiresome after the first half hour. People looking to conceal a weapon effectively, like spies and the like, are going to carry something small like a Kel-Tec .380 or a Sig-Sauer P365x 9mm. Professionals will stick to common calibers that can be readily found, like 9mm or .40 S&W or .45ACP (.32 ACP or .38 special in early 20th century.) this isn’t just so you can find ammo you need; the more common the caliber, the more likely the police won’t solve a crime. Unless you have a suspect, and you find the weapon — most 9mm shootings with no witness and no weapon go unsolved, these days.
Statistically, most assailants are incapacitated with 2.5 rounds from a handgun, 2 from a rifle, and 1.25 rounds from a shotgun. The movie trope of dropping a guy with a single shot — that only really happens in less than a quarter of shootings. You’re certainly not dropping a helicopter with a Walther PPK in .380.
Some tidbits to help with realism on failed rolls: Autos usually throw their shells to the right, but occasionally they won't — Lugers threw them straight up and back; that’s why German soldiers shot them with their hand canted at an angle. Either way, a failed roll could be because a shell bounced off something (if indoors) and you got hot brass in the face. Some weapons like the P90 drop their shells straight down, as not to distract the shooter. or the shell will bounce off of something. Nothing is worse than hot brass down a shirt or caught under the bridge of your eyeglasses.
Browning Hi-Powers, most CZ-75s, the FN57 all have magazine safeties. If the mag isn't seated (or seated properly) the gun will not fire. So if you're changing magazines with one in the pipe, you can't fire that single round. For critical fail/fumbles, you might consider the magazine got knocked loose (especially left handed folks can catch the magazine release button -- if on the side of the handle -- by accident and unseat the mag.) One interesting pistol in the H&K P7: it's squeeze cocked by depressing the front strap. An NPC that got your P7 from you might not know this...and not be able to fire right away. I've used all of these things in a game.
Other tidbits: Desert Eagles tend, after firing a while, to have their safeties self-engage; the recoil makes the lever drop down and lock the gun. For the "I've gotta have a big gangsta gat" types, this is a great malfunction to pop on them. I've seen rifles and pistols where tight tolerances or over-oiling lock the spent casing in the breech due to heat expansion -- in these cases, clearing the jam can take minutes. (I had a P9S that had to have the magazine removed and the butt of the pistol slammed on something to work the slide and clear the casing. Needless to say, I traded the thing, sharpish.) A revolver CAN jam, but it's usually an ammo problem -- the shell can have the primer expand and catch the firing pin, or prevent the cylinder from moving.
Most malfunctions in autos are due to 1) magazines -- either the spring isn't pushing the rounds properly and they need cleaned and maintained, or discarded; 2) the extractor spring is bad and the shell casing isn't being throw clear; 3) ammunition -- either "dirty" (smoky, oily, nasty smoke clouds) that bind up the action with carbon, or underloaded, which might make the action not run far enough to pick up the next round, or — in the worst case scenario — leave a bullet lodged in the barrel. This is called squib round and the next round fired can blow the gun up. Overloaded ammo, which generates too much pressure and might run the slide on an auto too fast too reliably pick up the next cartridge, can cause a primer blowout on a revolver, or blow the barrel out.
Most revolver issues are either ammunition, or something to do with the cylinder timing or lockup -- if the cylinder doesn't rotate or lock properly, the bullet could hit the barrel and destroy the gun.
That's just some spitballing on the subject to aid GMs looking for a more “real” approach to firearms in games.