1) Can someone tell me what a standard army issue assault rifle would be? 2) And, for someone who has never even held a gun, how does it work? 3) How do you fire it and load it? 4) Does it have a safety catch? 5) Anything else I really ought to know? 6) Any slang I should be aware of?
7) what's the difference between semi-automatic and selective fire?
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Bolded numbers added to the above quotes.)
I think you have adequate answers already for the following questions: 1, 4, 7. Here are some thoughts on the rest, according to the question number. Brace yourself, this is going to get long.
#2 and #3: Combined due to similarity. Different guns work differently (and are loaded/fired differently), but here is the basic idea common to most firearms.
Modern guns are made of metal, often with wood or polymer parts to reduce weight or maintenance. Non-metal parts will be those which don't have to take as much stress. Despite rumors and pipe dreams, there are no guns commercially available or in widespread military use that do not include metal.
Basic gun parts. Not all guns conform to these images (notably, bullpup designs like the
P-90), but they cover enough to be a great starting point. The page I linked to isn't the most beginner-friendly description, but do read it as it has details I won't cover here.
The
stock is placed in the inside 'curve' or 'hollow' of the shoulder. This is to help the shooter deal with
recoil (explained later), allowing better accuracy, among other things.
From your comments, I'm going to assume you understand the functions of a
safety and the
trigger. The
trigger guard literally guards the trigger from accidentally being pushed.
In a very broad sense, the
action contains the bolt, the receiver, and all the other parts that make the gun actually do anything. This gets complicated and isn't required for a basic overview; feel free to look up these parts on your own if you wish. Various parts of the action can be gummed up with dirt, grime, etc. Failure to keep these parts clean can result in malfunctions. Modern guns, particularly those deployed in militaries, are designed to work even when dirty, but there are limits to what a gun can handle (and for how long) before issues manifest. Many military movies show soldiers dismantling and reassembling their rifles- this is because real-world militaries do train for this, helping soldiers maintain their weapon in the field or quickly clear a jam. The repetitive training may serve other, more psychological, purposes as well.
The
barrel is where the bullet goes once fired. After repeated, rapid firing, a barrel will heat up. The length of a barrel is important for long-range accuracy: longer generally means more accurate. Shorter barrels allow for more rapid responses in close-quarters combat (the P-90 I linked above is one such design).
A
scope can be mounted atop the barrel, usually where the picture says "rear sight." You do not place your eye right next to the scope when firing, as the scope is attached to the rifle and will hit your face when the weapon recoils. Scopes come in many types, from basic (think binoculars on the gun) to infrared or laser sights.
An
iron sight, or simply
sight, is used to aim when no scope is attached. Two sights are placed on top of the barrel; lining the two up visually with the eye, so your eye makes a straight line to the rear sight, which makes a straight line to the front sight, enables a shooter to aim properly. Firing without use of a scope or the sights is almost always much less accurate (and is often called "firing from the hip").
The
muzzle is the end of the barrel. This is where a
silencer (more accurately, a
suppressor) may be attached. No gun shot can be silenced completely, but the noise can be reduced (typically by 20-40 decibels, for example from 160 to 135 decibels). Suppressors often hide the "muzzle flash" (a flash of light seen at the muzzle when a bullet is fired).
A
bullet, cartridge, round, or shell are all terms used somewhat interchangeably by most people to describe the projectile fired from a gun and the propellant used to fire it. When the trigger is pulled, the propellant (also called powder) is ignited. This burns so fast it is often mislabeled as an explosion. The force, combined with the very confined space, pushes the small projectile forward at incredible speeds. If desired,
here is more detail on this process.
A cartridge can be manually loaded into the bolt (particularly true for most shotguns, or for rifles that do not use a magazine). Otherwise, cartridges are loaded into a magazine.
Once 'fired', the gun ejects the spent
shell casing (a lever-action or bolt-action rifle does not do this automatically, but this style of rifle is increasingly uncommon among militaries, save for snipers). This shell casing is quite hot, though cools quickly. Once the shell casing is ejected, the gun needs to be loaded again. In a pump-action shotgun, you "
pump" to load a new cartridge. Most modern rifles and pistols will load another cartridge automatically, while a revolver rotates to the next bullet.
A
magazine simply holds cartridges, ready to be loaded automatically when needed. A pump-action shotgun typically holds between 4-8 (sometimes more) cartridges. A revolver typically holds 5, 6, or 8. A pistol typically holds between 5-12, and a rifle can hold between 5 (for hunting rifles) to 30 or more cartridges. The magazine is "clicked" or locked into place, usually but not always on the underside of the barrel. Once a magazine is in place, the gun must be cocked (or pumped) manually, but only once. This loads a single cartridge in place. (Bonus: this is the origin of the phrase "half-cocked", when you jump into something without being fully prepared.)
As noted by others above, an
automatic weapon is any weapon that can automatically load and fire a cartridge one after another, as long as the trigger is depressed.
Semi-automatic designates a weapon that can automatically load a new cartridge but will not fire unless the trigger is depressed for every shot. These two terms can be used to describe any weapon, not just rifles or pistols. Automatic firearm firing is inaccurate.
Recoil is the force of a gun moving away from a fired cartridge. A bullet travels out of the gun very fast, but is also small. Hence a shooter will not fly backwards after firing a shot, and a human hit by a bullet will also not fly backwards after being hit. But recoil can hurt, particularly if the stock is not placed against the shoulder properly (or if a pistol or scope is held too close to the face). Being hit with your own scope is referred to as "being scoped" and is not uncommon among new shooters, but is very rare for anyone with firearm training.
Caliber, or
cal, is a description of cartridge size. Larger calibers use more propellant to fire a larger projectile, which results in more recoil, but also more damage to the target.
Most modern firearms can fire in a vacuum or even underwater. However, water generates
much more friction than air; bullets in water lose their speed very rapidly, resulting in the bullet only going through 2-20 feet of water (depending the caliber used and other circumstances) before coming to a complete stop. Bullets in water may also disintegrate from the increased friction, leaving naught but small pieces of metal behind. Firearms not designed for underwater use will not fire reliably underwater.
Bullets travel quickly, but they are not instantaneous. A variety of factors impact accuracy, particularly at long range, because the bullet is affected by them. Wind speed and direction, humidity, gravity, and other conditions must be accounted for by anyone firing at long ranges. This means snipers usually work with a teammate (called a spotter), and snipers are often very good at calculating and compensating for these factors. Most soldiers do not encounter such long ranges often enough for extensive training in these techniques.
Bullets penetrate some objects better than others. Larger calibers typically penetrate better. Wood planks and sheet rock are usually insufficient protection from a rifle or even a pistol. Cinderblocks are not always able to stop rifle rounds, but are better. Solid concrete, thick wood, sand bags, or dirt are best (or armored vehicles, thick steel, etc). The type of cartridge loaded into a gun can change how well it penetrates something.
There is no such thing as "bullet-proof" glass. Various types of glass, or clear materials like plastics, can withstand a certain number of hits from certain calibers of bullets. Even the best armored glass will eventually give way under a sufficient torrent of gunfire, assuming the caliber bullets being fired are large enough. The same can be said of body armor. Also, when body armor stops a bullet, the wearer usually still gets a nasty bruise, and sometimes worse.
In war, very few shots actually hit someone. Think 10,000 to 300,000 bullets per kill, depending on the war. The numbers are lower if you include injuries, and more like 2 bullets per kill for elite snipers.
#5: Depends on the needs of your story. If you aren't sure on something, feel free to ask!
#6: There is a ton of slang in every military, and a good amount of it revolves around guns and weapons. For your story, you will want to focus on interactions with certain characters. Pick a NATO country (or countries) these characters belong to and then ask this question, with the country(ies) named, in a new thread. You'll get much more focused, much better, results this way.
