Gun safety is a collection of rules and recommendations that can be applied when handling firearms. The purpose of gun safety is to eliminate or minimize the risks of unintentional damage, injury and/or death caused by improper handling of firearms.

The rules of gun safety follow from this mindset. While there are many variations, the following rules are those most commonly taught during gun safety training:

• Always treat firearms as if they are loaded and ready to fire.
• Always point the muzzle away from anything you do not intend to shoot.
• Always keep your fingers away from the trigger and outside the trigger guard until you are ready to fire.
• Always be sure of your target and of what is beyond it.

Always treat firearms as if they are loaded
This rule is a matter of proper mindset rather than a specific habit. Many firearm accidents result from the handler believing a firearm is emptied, safetied, or otherwise disabled when in fact it is ready to fire. Such misunderstandings can arise from a number of sources.

• Faulty handling of the firearm. A handler may execute the steps of procedures such as loading, firing and emptying in the wrong order or omit steps of the procedures.
• Misunderstandings about a firearm's status. For instance: A handler may think the safety is on when it is not; A round of ammunition may be in the chamber or in the magazine while the handler thinks it is empty; A handler may receive a firearm and assume it is in a certain state without checking whether that assumption is true.
• Mechanical failures. Wear, faulty assembly, damage or faulty design of the firearm can cause it to not function as intended. For instance: A safety may have been worn down to a point where it is no longer functioning. Broken parts may have given the firearm a "hair trigger" (a very sensitive trigger). A dented or bent body of the firearm may cause jams or premature discharge of ammunition. Sensitivity to impact may cause a firearm to discharge if dropped or struck against another object.

If a handler always treats firearms as capable of being fired at any time, the handler is more likely to take precautions to prevent an unintentional discharge and to avoid damage or injury if one does occur.

The phrase "The gun is always loaded" is often used. The purpose is to discourage mental habits such as "I know my gun is empty so (some) unsafe practices are OK." Inexperienced handlers often think this way and accidents can happen as a result. A gun safety instructor can respond to such reasoning by restating the rule: "No, your gun is always loaded".

Point the muzzle away from non-targets
This rule is intended to minimize the damage caused by an unintended discharge. The first rule teaches that a firearm must be assumed to be ready to fire. This rule goes beyond that and says "Since the firearm might fire, assume that it will and make sure no harm occurs when it does".

A consequence of this rule is that any kind of playing or "toying" with firearms is prohibited. Playfully pointing firearms at people or other non-targets violates this rule.

Two natural "safe" directions to point the muzzle are upwards (at the sky) and downwards (at the ground). Both have their advantages and disadvantages. Firing at the ground may result in a ricochet or cause hazardous fragments to be flung at people or material. Aiming upwards eliminates this risk but replaces it with the risk that the bullet may cause damage when it comes down to the ground again. Indeed, several accidents have been caused by discharging firearms into the air. It is also possible that the muzzle will inadvertently be pointed at a non-target such as someone's head or an aircraft.[1]

When passing a firearm to another person, it should be passed such that the muzzle of the weapon does not point at, or "flag", the recipient or any bystander. If the situation permits it is considered good practice to show the firearm with the magazine removed, the breech unloaded and locked open before handing it over to the recipient. This is known as "show clear". The recipient should personally check the firearm upon receipt, even if he has seen it clear while in someone else's possession.

Keep fingers off the trigger
This rule is intended to prevent an undesired discharge. Normally a firearm is discharged by pressing its trigger. A handler's finger may involuntary move for any of several reasons: being startled, not keeping full attention on body movements, or physiological reasons beyond conscious control such as spasms. Handlers are therefore taught to minimize the harmful effects of such a motion, by keeping the finger off the trigger.

The trigger guard and area above the trigger of a firearm presents a natural point for a handler to keep their finger out straight alongside the weapon, so as not to violate this rule (see picture above). A properly indexed trigger finger also helps remind the person holding the gun of the direction of the muzzle.

In popular culture, such as movies and TV shows, this rule is often violated, even by characters who would be trained in gun safety such as military personnel or law enforcement officers.

Be sure of your target - and of what is beyond it
This rule is intended to eliminate or minimize damage to non-targets when a firearm is intentionally discharged. Unintended damage may occur if a non-target is misidentified as a target, or if the bullet hits something or someone other than the intended target.

Handlers are taught that they must positively identify their target as valid. Additionally, they learn that even when firing at a valid target, unintended targets may still be hit, for two reasons:

• The bullet may miss the intended target and hit a non-target.
• The bullet may pass through the intended target and hit a non-target beyond it, so called "overpenetration".
  

This may create situations that present dilemmas for a handler. Such situations are for instance a police officer in a riot or a soldier in a situation where civilians are near the enemy. Indecision or misjudgment of the handler's abilities in such a situation may cause undesired outcomes, such as injury to the handler or the handler violating rules of engagement and causing unintended damage.

To mimimize the risk of such outcomes training is required. Target practice increases the precision with which the handler can discharge the firearm and thus increase the chances that the intended target is hit. Education about terminal ballistics gives the handler knowledge about the characteristics of a bullet after a target is hit. This knowledge coupled with insight into the handler's own capabilities makes it easier for the handler to make appropriate decisions about whether to fire or not, even if given little time and/or put under severe stress.