Difference between revisions of "Safety (device)"

Latest revision as of 15:56, 15 March 2013

This article is about the mechanical safety devices built into most (but not all) firearms. For the main article about firearm safety education, see Gun safety.

Close-up shot of a safety of an M16A2 rifle.

In firearms, a safety or safety catch is a mechanism used to help prevent the accidental discharge of a weapon, helping to ensure safer handling.

Safeties can generally be divided into subtypes such as internal safeties (which typically do not receive input from the user) and external safeties (which typically allow the user to give input, for example, toggling a lever from "on" to "off" or something similar). Firearms with the ability to allow the user to select various fire modes, from 0 (safe/off/no firing) to 1 (semi-automatic fire) to 2 (burst fire) to 3 (full-automatic fire), usually have a dial-type external safety that is called a fire selector, fire mode selector, etc.

Many guns manufactured after the late 1990s include mandatory integral locking mechanisms that must be deactivated by a unique key before the gun can be fired. These integral locking mechanisms are intended as child-safety devices during unattended storage of the weapon — not as safety mechanisms while carrying. Other devices in this category are trigger locks, bore locks, and gun safes.

[edit] Typical safeties

[edit] Manual Safety

The most common form of safety mechanism is a switch that, when set to the "safe" position, prevents a pull of the trigger from firing the weapon. Designs of such safeties are as varied as the designs of handguns themselves, but the two most common mechanisms are a block or latch that prevents the trigger and/or firing mechanism from moving, and a device that disconnects the trigger from the firing mechanism of the weapon. These are one of the oldest forms of "active" safety mechanism and are widely used; however many "double action" weapons such as revolvers do not have them as the longer, harder trigger pull to cock and fire such a weapon provides adequate trigger safety, while keeping the weapon in a more ready state.

[edit] Grip Safety

A grip safety is a lever or other device situated on the grip of a weapon which must be actuated by the operator's hand as a natural consequence of holding the weapon in a firing position, in order for the weapon to fire. It is usually similar to a manual safety in its function, but is momentary; the safety is de-activated only while the shooter maintains their hold on the grip, and is re-activated immediately once the shooter releases it. The Browning M1911 design is a popular example of a handgun with a grip safety. The Uzi submachine gun is another example of a firearm with a grip safety.

A related grip-type safety is the decocking grip found on some H&K pistols like the P7 Series. The weapon is cocked and ready to fire only when the front of the grip is squeezed by the operator. When the grip is released, the weapon is decocked, and the single-action trigger will not cock the weapon, therefore it will not fire unless the grip is squeezed and the trigger pulled.

[edit] Decocker

Traditional Double-Action (DA/SA) semi-automatic pistols are designed to be carried with the hammer down (De-cocked) on a chambered round, with or without a safety engaged. The pistol is considered safe in this state even without a manual safety engaged as the trigger requires significant force over a longer travel to both cock and fire the weapon than when the hammer is cocked. However, the act of chambering a round on such a weapon automatically cocks the hammer. In some designs, it is necessary to hold the hammer and carefully control its movement to the down position while pulling the trigger, in order to avoid an unintentional discharge.

A Decocker or decocking lever allows the hammer to be dropped on a live cartridge without discharging it, via disengaging, retracting, blocking or covering the firing pin. This eliminates the need to control the fall of the hammer, although since all mechanisms can fail it is still necessary to keep the muzzle of the gun pointed in a safe direction while operating the decocker.

A decock/safety is a combination manual safety and decocking lever. Two popular variants exist: one allows the user to decock by moving the switch one way from a neutral position, or engage the safety on a cocked weapon by moving the switch the other way (thus allowing the user to carry the firearm "cocked and locked"); the second decocks the weapon when the safety is engaged (which prevents such carry, but is generally safer as both the safety and the double-action trigger pull lower the chance of accidental discharge).

Examples of a decocking lever are many of the Sig Sauer line of pistols such as the SIG P226. The earliest use of single action decocker was the Vis Wz 35 redesign in 1932 to enable horsemen to safely holster their weapon with one hand.^[1] The earliest use of a cocking/decocking lever is the Sauer 38H from 1938. Ruger until 2007 manufactured "decock-only" variants of its P-series pistols, and has always incorporated the decocking feature into its manual safeties on these pistols; moving the switch to safe decocks the weapon as well as engaging the safety mechanism.

[edit] Drop Safeties

Many jurisdictions such as the State of California require some form of "drop safety" on all new firearms. A drop safety, as the name implies, is designed to reduce the chance of a weapon accidentally discharging when it is dropped or roughly handled. Such safeties generally provide an obstacle to proper operation of the firing mechanism that is only removed when the trigger is pulled, meaning any other possible cause of the weapon discharging is generally prevented.

[edit] Firing Pin Block

A firing pin block is a mechanical block used in semi-automatic firearms and some revolvers that normally impedes forward travel of the firing pin, but is linked to the trigger mechanism and clears the obstruction to the pin just before the hammer or striker is released. This prevents the firing pin from striking a chambered cartridge unless the trigger is pulled, even if the hammer is released due to a faulty sear or the pin is struck by another object.

[edit] Hammer Block

A hammer block is similar to a pin block but is used in revolvers, and is a latch, block or other obstruction built into the action and normally positioned to prevent the hammer contacting the cartridge primer when at rest. The obstruction to the hammer's travel is removed as a consequence of pulling the trigger, allowing the hammer to contact the primer only when the trigger is pulled.

[edit] Transfer Bar

A transfer bar is also used in revolvers, but works the opposite way from a hammer block. The transfer bar, in a weapon so equipped, features the spur that would otherwise be found on the hammer, or encloses a firing pin similar to autoloading designs. The hammer itself cannot contact a loaded cartridge; it must instead strike the transfer bar, which then contacts the cartridge primer with the spur or pin. The transfer bar is normally positioned out of line with the hammer's travel, but is moved into place by the normal action of the trigger, providing similar "drop safety" to a firing pin block.

[edit] Bolt Interlocks/Trigger Disconnects

Popular on bolt, pump and lever-action firearms such as shotguns and rifles, a bolt interlock disengages or blocks the trigger if, for any reason, the bolt/breech is not in its fully closed, ready position. A variation is the trigger disconnect which prevents the gun from firing until the gun has not only been fully and completely cycled, but the trigger is released and squeezed again. This defines the behavior of semi-automatic firearms which require a separate trigger pull to fire each successive cartridge and ready the next, and this is the preferred mechanism of disengaging the trigger on repeating-action weapons. Older pump-action shotguns such as the Winchester Model 12 did not have such a feature, and as a result if the trigger was held the newly chambered round would be fired as soon as the breech had been closed.

Such disconnects or interlocks are generally simple to incorporate, and in fact are a by-product of many firearms' actions; pulling the trigger while the breech is unlocked or open does nothing as the mechanism is not fully reset until cycling is complete. As such these features are often not considered "true" safeties, although the interlock helps prevent misfires due to a bullet not being fully in the breech when its primer is struck by the pin (known as firing "out of battery"), and passing handguns or rifles to another person with the action open (known as "show clear") is recommended by elementary gun safety.

[edit] Magazine Interlocks

A magazine disconnect is an internal mechanism that disconnects the trigger of a firearm when its magazine is removed. As with any firearm feature, there is debate regarding the necessity of a magazine disconnect. Most magazine-capable firearms have no magazine disconnect. There are exceptions, notably Ruger rimfire rifles, and the U.S. State of California passed legislation in 2006 requiring magazine disconnects on all new handgun designs sold in the state starting January 1, 2007.

The arguments in favor of a magazine disconnect are that if the gun cannot fire without a magazine, then an accidental discharge can be prevented if someone removes the magazine but forgets that a round has been chambered. Also, if losing possession of the firearm is imminent, the operator can render the firearm useless by removing the magazine.

The arguments against a magazine disconnect are that without a magazine the firearm is useless except as a club. Without the feature, if a magazine was lost or otherwise not available, then at least the gun could be chambered with a single round to be used as a single shot weapon. From a technical standpoint, a magazine disconnect adds extra parts to a weapon and thus increases complexity which creates additional risk of component failure while potentially increasing production costs. In some cases, the disconnect adversely affects trigger feel, and hence affects accuracy.

Some experienced firearms operators see little value in having a magazine disconnect due to their belief that proper firearm handling and care offer equal safety. Some also see magazine disconnects being introduced as a way to appease anti-gun politicians, while lessening firearm accuracy, reliability, and safety (for always keeping a defensive weapon ready to fire, even during a tactical reload during a firefight.)

[edit] Integrated Trigger Safeties

These safeties, similar to grip safeties, are de-activated as a natural consequence of the shooter firing the weapon, but are engaged in most other circumstances. The trigger is composed of two interdependent parts, and the shooter in firing the weapon manipulates both parts of the trigger. Conversely, unintentional pressure or a strike against the trigger is unlikely to do so, and such an action will not fire the weapon. Such a design, made popular by Glock pistols, incorporates a trigger with a spring-loaded lever in its lower half. This lever which protrudes from the trigger face must be fully depressed in order to disengage a lock that allows the main trigger body to move. Unintentional pressure against the trigger without pressing the lever does not disengage the lock and the trigger will not move. Other designs include a spring-loaded pad that forms the upper portion of the trigger face and manipulates a similar lock. This design has more moving parts, but is advantageous in that accidental pressure on the lock release has reduced leverage thus requiring more force to pull the main trigger, where force against the lower portion does not release the lock and will not move the trigger.

[edit] Other Safeties

Examples of the variety of typical semi-auto mechanisms are a stiff double-action trigger pull with the safety off (Beretta 92), a double-action with no external safety (SIG-Sauer P-series, or Kel-Tec P-32), or a crisp single action trigger pull with a manual safety engaged (M1911 and certain configurations of the HK USP). An alternative are striker-fired or "safe action" type weapons which have a consistent trigger pull requiring force greater than required by a single-action design, but lighter than needed for a double-action trigger. Many such weapons do not have an external safety or external hammer (Glock pistols and the Walther P99 and variants). In both cases, the action is very simple—a trigger pull always sends a discharge—and there are internal safeties to prevent non-trigger-pull discharge (e.g., dropping the gun).

[edit] Controversy

While some form of safety on a firearm is advocated by the majority of firearms owners, the number and type of safeties incorporated in a gun's design has almost always been a source of controversy. Quite simply, safety mechanisms add complexity to the weapon and increase the chances of a mechanical failure either allowing an accidental discharge or preventing an intentional firing of the weapon. In addition, many safeties such as manual safeties slow the process of readying the weapon as the user must consciously de-activate that safety. Opponents of new types of safeties cite these facts, and state that the four rules of gun safety, if strictly followed, would remove any necessity for safety mechanisms.

Proponents of safety mechanisms state that no matter how careful a gun owner is, accidental/unintentional discharges can and do occur. Safety mechanisms reduce the chances of an accidental discharge when a gun is mishandled or its controls are unintentionally manipulated, such as during a draw from a holster, reholstering the weapon, accidental drops or even negligent mishandling. In addition, a user can be trained to remove a manual safety very quickly, so it provides little impediment to intended firing of the weapon in the hands of a knowledgeable user.

A common situation used to argue for or against a manual safety is a nighttime intruder when the user is sleeping. Having been suddenly awoken and not fully alert, opponents say, the user may not have the presence of mind or the manual coordination to deactivate the safety when a split second could make the difference between life and death. Proponents argue that if that is the case, the user would also not be alert or aware enough to identify his target or surroundings, resulting in an accidental shooting.

In any case, proponents argue, a gun that is otherwise considered safe with the external safety deactivated or non-existent (such as a weapon that requires a stiff double-action trigger pull in its current state) can simply be kept ready with the safety disengaged, but that the choice of having an external safety should reside with the user, not the designer or the state.

[edit] Firearms

[edit] Pistols

Almost all modern handguns, except some exact replicas of antique models, have safeties to prevent accidental discharge including one or more safeties that require an intentional trigger pull to make the gun discharge. However, the exact configuration depends on handgun type, year, make, and model.

[edit] Double-action revolvers

On almost all double-action revolvers, there are no external safety devices; a trigger pull will always result in firing, unless the chamber being indexed into battery is empty. In general, the heavy trigger pull required to cock and then fire the weapon prevents accidental discharges from dropping or mishandling the gun. In addition to that fact, most modern double-action revolvers do have an internal safety, either a hammer block or a transfer bar, that prevents firing not originating from a trigger pull (e.g., gun is dropped).

The only double-action revolvers with external safeties are unusual cases via special order or aftermarket conversion.

[edit] Single-action revolvers

Single-action revolvers have no external safeties, and they usually have no internal safeties, such as a hammer block or transfer bar, to render them drop-safe. Real antiques are in this category; modern replicas may have hammer blocks. Therefore, carrying them with a loaded chamber under the hammer is not safe. When they are carried (concealed or openly), the hammer should be left down on an empty chamber.

However, some single-acton revolvers have relief cuts in between cylinder bores that allow the hammer to be laid to rest directly upon the cylinder with no chance of interacting with loaded cartridges or primers. These are also known colloquially as “safety notches.” They are usually found on black powder revolvers, but there are cartridge firing revolvers that utilize safety notches as well.

[edit] Rifles

Rifles come with various safeties. Some use a cross-bolt safety button, others a wing safety at the rear. The M1 Garand created a safety with a metal rocking lever at the front of the trigger guard that is now called the Garand-style safety.

Some rifle safeties have two positions, one which is "safe" which doesn't allow the gun to fire or the action to open. Some have three positions, one which is "fire", one which is "safe" and an intermediate which cannot fire but will allow the shooter to open the action in order to empty the rifle.

[edit] Shotguns

Some shotguns use button-style safeties behind the trigger guard. Tang safeties (a switch placed at the top rear of the receiver) are also very common for shotguns.

On the SPAS 12 there was a problem with the safety, which meant if there was a shell in the chamber and the safety was changed to safe the weapon would discharge.

[edit] Aftermarket modifications

Certain handguns that come from the manufacturer with no external safety lever (on-off/armed-safe), such as double-action revolvers and Glock pistols, can be modified by aftermarket companies who add one at the user's request.

[edit] See also

• Firearm
• Gun safety

[edit] References

1. ↑ "The Radom Pistol" by Robert J. Berger (cf. p. 10)