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All firearms operate under the same basic principle: there is a frame which holds the firearm parts, a mechanism for holding ammunition in-place, an ammunition feed process to align unspent ammunition in front of the firing pin, a trigger which releases the firing pin, and a barrel which directs the bullet towards its intended target or direction in which the firearm is pointed.
Modern firearms share very common characteristics. Every firearm operates on what can be described as a closed-tube system. Essentially, the "tube" is the "barrel" of the firearm, which has a closed side and an open side. The closed side is closest to the user and is the area in which ammunition is loaded; the open side is the area farthest from the ammunition in which the bullet is expelled towards its target.
Basic Bullet Components
Bullets are simple in design. They contain a propellant known as gunpowder, which is encased within a metal casing. At one end of the bullet case, a small amount of primer is present, which creates a spark when struck by the firing pin. At the other end, the projectile, or bullet, typically brass coated lead, is present and machine pressed into the casing. Gunpowder is highly flammable, and when ignited, creates a high level of gas within the bullet casing, causing the bullet, or projectile to "escape" or be release from the bullet casing, down the barrel, and towards its target.
Breech Loaded Pistols
Modern pistols that shoot metallic cartridges are known as "breech loaded" firearms. The name is applied because all ammunition is loaded into the firing position at the rear end, or breech end, of the barrel. Pistols, therefore, must allow a method in which ammunition can be loaded from the breech end and yet protect the user from the gasses that release when a bullet is fired. The mechanism for protecting the user varies, however, the goal is the same: prevent discharged gasses from "blowing back" towards the user. When this goal is accomplished, the system is known to be a closed system.
Common Pistol Components
Pistols share common components which consist of: The Frame, Barrel, Trigger, Safety Mechanism, and Locking Mechanism.
Most firearms have a built-in safety feature which prevent unintended discharges. However, the best safety mechanism is the gun owner. If their finger is not on the trigger, the gun will not discharge. Gun owners who claim there was an "accidental discharge" can never explain why their finger was on the trigger--that is an excuse. Your finger should never be on the trigger until you have acquired your target, made sure there's nothing beyond the target that can get hit, and you have made the decision to fire your gun.
Pistols have different actions which must be performed before they can be fired.
Single Action Pistols: A single action pistol requires the manual cocking of the hammer before a bullet is moved into position and the trigger can be pulled.
Double Action Pistols: Double action pistols require a full pull of the trigger to load, cock, release the hammer, and expel ammunition.
Semi-Automatic Pistols: Semi-automatic pistols require an initial pull of the slide, which loads the bullet and prepares the gun to fire. When a semi-automatic pistol is fired, the gases from the bullet causes the slide to repel backwards, the spent shell to be released via the ejector mechanism and a new, unspent shell to be loaded into the chamber. The slide returns back to its original position ready for use.
As a result, if your finger is not on the trigger, the gun will not fire. ALWAYS keep your finger off the trigger until ready to shoot!
The pistol frame is the central component in which all parts are attached. The frame must be strong enough to withstand the pressure exerted on it when a bullet is fired and support the action of the parts attached to it, such as the cylinder (revolvers) or the slide (semi-automatics). For revolvers, the barrel is part of the frame whereas on semi-automatic pistols, the barrel is generally a separate component attached to the frame. Additional parts, such as the grips and sights may be added to the frame when it gun is being built. Today’s modern frame is commonly made from polymer materials which reduces the overall weight of the gun. Traditional frames are made of steel, aluminum, or titanium depending on the manufacturer’s choice.
It's interesting to note, a closed system, although a technically correct term, does not truly exist. When the bullet is fired, when the gunpowder is ignited, when the gasses erupt, a small level of gunpowder residue escapes from the rear of the barrel and presents itself on the shooters hands and face. CSI enthusiast know the detection of this residue is known as "Gun Shot Residue" or "GSR" for short.
In its most basic form, the barrel is a simple tube, usually made from steel, in which the bullet travels through after the gun has been fired. The barrels job is to ensure the bullet is directed towards the intended target and away from the operator.
The inside area of the barrel is called the bore, which has a series of spiral grooves known as rifling, spins the bullet as it leaves the barrel. The area on top of the grooves is referred to as lands.
At the rear of the barrel is the chamber. The chamber is a section of the barrel that is enlarged to exact specifications to accept the caliber ammunition the gun is designed to discharge.
Comparison of Major Pistol Parts
The trigger is the component of the gun that immediately releases the hammer, firing pin, or striker directly, or in some guns indirectly, through an intermediary mechanism such as a sear or a trigger bar. The trigger is located directly in front of the gun grips and is protected by a trigger guard which prevents unintended discharges from occurring. The trigger is slightly curved with a smooth finish to accommodate the trigger finger comfortably.
It’s important to note not all triggers are the same distance from the pistol grip. Depending on the size of the gun, the trigger can be far away from the frame or extremely close. Some frames allow you to change the grip which allows for a slight increase or decrease in the size of the grip and hence a slightly closer or further distance from the trigger can be achieved. When purchasing a handgun, be aware of the position of the trigger and where the top-pad of your index finger rests on the trigger. Ideally, the finger should meet the trigger in the middle of the top-pad of your finger. If you need to stretch, you’ll find you will need to train yourself a little bit longer to achieve accuracy. If the trigger is too close, this will also cause you to have to train a little bit longer to achieve accuracy.
As stated previously on this page and throughout our site, the best safety mechanism is not located on the gun, it's located on the shooters body; the finger. ALWAYS keep you finger off the trigger until you are ready to shoot and your safety mechanism will never fail!
There are, however, some very good features on guns which promote safety, such as the trigger guard, which helps to prevent an unintended discharge while holstering your gun.
Most guns have a feature called a safety switch, which can be activated or deactivated by sliding a button into the desired position. Depending on the function of the switch and the type of pistol it is mounted on, the safety can prevent the slide of a semi-automatic pistol from moving or the trigger on a revolver from being pulled into a firing position.
Passive safety mechanisms include the grip safety, which prevents the gun from firing unless it is held correctly in the hand. Other examples include preventing the hammer from hitting the firing pin or preventing the firing pin from hitting the cartridge unless the trigger is pulled back completely. Some guns feature a decocker which allows you to lower the hammer without firing the bullet.
No matter which safety features you gun has, be sure to familiarize yourself with them completely. You don't want a safety feature to prevent you from using your firearm during an emergency. Remember, all safety features can fail; keeping your finger off the trigger will never fail.
Breech Locking Mechanisms
Semi-automatic pistols close their breech via the slide, which rides back and forth on the frame of the gun. When the slide is forward, the breech is said to be closed as the slide protects and covers the chamber and ammunition. When the slide is back, the breech is said to be open as the chamber and ammunition are exposed and visible.
Revolvers do not have a separate breech lock. Revolvers have a flat face in the frame which is referred to as the recoil shield, which protects the head of the cartridge that is aligned with the firing pin and the barrel.
Common Pistol Actions
Single-action revolvers do not load ammunition when the trigger is squeezed, requiring the operator to pull back the hammer before each firing event. In a life-threatening situation, this is probably not the best type of revolver to have to protect yourself.
Double-action revolvers perform two steps simultaneously - they “cock” the hammer and rotate the cylinder at the same time. A double-action revolver will continue to rotate the cylinder, provide a fresh round of ammunition to the gun, and complete the firing sequence with one complete pull of the trigger. This is the type of behavior you’ll want when faced with a life threatening encounter.
Double-action only revolvers don’t have a “hammer” to cock. They rely on an internal firing mechanism and therefore, cannot be “manually cocked”. Aside from this exception, the double-action only revolver behaves in the same fashion as the double-action revolver. One benefit with double-action revolvers is the missing “hammer”, which makes the gun somewhat led likely to “snag” on clothing during presentation.