What are the internal mechanisms of a silencer?


If there is a hammer in its mechanism that strikes a metal plate at the end of its movement, a small piece of sound-absorbing material mounted on the plate will reduce this sound.You must calculate how much air expands in your gun's firing chamber.

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Trigger (firearms)
A trigger is a mechanism that actuates the firing sequence of a firearm. Triggers almost universally consist of levers or buttons actuated by the index finger. Some variations use the thumb or weak fingers to actuate the trigger, a feature typically found on mounted weapons. Examples are the M2 Browning machine gun and the Springfield Armory M6 Scout. Firearms use triggers to initiate the firing of a cartridge in the firing chamber of the weapon. This is accomplished by actuating a striking device through a combination of spring and kinetic energy operating through a firing pin to strike and ignite the primer. There are two primary types of striking mechanisms, hammers and strikers. Hammers are spring-tensioned masses of metal that pivot on a pin when released and strike a firing pin to discharge a cartridge. Strikers are, essentially, spring-loaded firing pins that travel on an axis in-line with the cartridge eliminating the need for a separate hammer. The connection between the trigger and the hammer is generally referred to as the sear surface. Variable mechanisms will have this surface directly on the trigger and hammer or have separate sears or other connecting parts. There are numerous types of action, which is the logic of how the mechanism is built and how it is used (where the mechanism is the trigger, hammer, and safeties considered as a unit of interconnected parts). They are categorized according to which functions the trigger is to perform. In addition to releasing the hammer or the striker, a trigger may cock the hammer or striker, rotate a revolver's cylinder, deactivate passive safeties, select between semi-automatic and full-automatic fire such as the Steyr AUG (see Progressive trigger), or pre-set a 'set trigger'. Most modern firearms use the trigger to deactivate passive safeties but this does not change how they are identified. A single-action (SA) trigger performs the single action of releasing the hammer or striker to discharge the firearm each time the trigger is pulled. Almost all rifles and shotguns use this type of trigger. Single-action revolvers such as the Colt Dragoon Revolver require the hammer to be cocked by hand every time the weapon is fired. Single-action semi-automatic pistols, such as the HS2000 (Springfield XD and XDm), require that the hammer be cocked before the first round can be fired, although most designs cock the hammer as part of the loading process (e.g., the act of inserting the magazine and operating the slide mechanism to chamber the first round also cocks the hammer or striker into the ready-to-fire position). Once the first round is fired, the automatic movement (recoil) of the slide cocks the hammer for each subsequent shot. The pistol, once cocked, can be fired by pulling the trigger once for each shot until the magazine is empty. The M1911 and Browning Hi-Power are single-action pistols that function in this manner. A double-action, also known as double action only (DAO) to prevent confusion with DA/SA designs, is similar to a DA revolver trigger mechanism. The trigger both cocks and releases the hammer or striker. However there is no single action function. A good example of this action is the SIG Sauer DAK trigger. For semi-automatic pistols with a traditional hammer (that employ only the double action function of the trigger), the hammer will return to its decocked position after each shot. Subsequent shots require the double action trigger firing sequence. For striker-fired pistols such as the Taurus 24/7, the striker will remain in the rest position through the entire reloading cycle. This term applies mostly to semi-automatic handguns; however, the term can also apply to some revolvers such as the Smith & Wesson Centennial, the Type 26 Revolver, and the Enfield No. 2 Mk I revolvers, in which there is no external hammer spur. Glock and Kahr semi-automatic pistols are not DA (or DAO) pistols because the striker is "cocked" to an intermediate position by the operation of the slide and they cannot be re-activated by pulling the trigger a second time. A double-action/single-action (DA/SA) firearm combines the features of both mechanisms. Often called traditional double action, these terms apply almost exclusively to semi-automatic handguns. The function of this trigger mechanism is identical to a DA revolver. However, the firing mechanism automatically cocks the hammer or striker after the gun is fired. This mechanism will cock and release the hammer when the hammer is in the down position, but, on each subsequent shot, the trigger will function as a single action. The Mateba Autorevolver is a semi-automatic revolver that functions on a DA/SA system. The Beretta 92 is a good example of a DA/SA semi-automatic pistol. On many DA/SA pistols (including the Beretta), there is the option to cock the hammer before the first shot is fired. This removes the heavy pull of the double-action. Also, there is often a de-cocker to return the pistol to double-action. A second distinct type is that used by the majority of double-action revolvers, where the weapon can be fired in either double-action mode by pulling the trigger, or single-action mode by cocking the hammer manually before firing. This is distinct from double-action only, since the weapon does not have to be fired in double-action mode, for example, the Colt Python. A release trigger releases the hammer or striker when the trigger is released by the shooter, rather than when it is pulled. Release triggers are largely used on shotguns intended for trap and skeet shooting.][ A set trigger allows a shooter to have a greatly reduced trigger pull (the resistance of the trigger) while maintaining a degree of safety in the field compared to having a conventional, very light trigger. There are two types: Single Set and Double Set. A Single Set Trigger is usually one trigger that may be fired with a conventional amount of trigger pull weight or may be 'set' – usually by pushing forward on the trigger, or by pushing forward on a small lever attached to the rear of the trigger. This takes up the creep in the trigger and allows for a much lighter trigger pull. As above, a double set trigger accomplishes the same thing, but uses two triggers: one sets the trigger and the other fires the weapon. Set triggers are most likely to be seen on customized weapons and competition rifles where a light trigger pull is beneficial to accuracy. Double set triggers can be further classified by phase. A double set, single phase trigger can only be operated by first pulling the set trigger, and then pulling the firing trigger. A double set, double phase trigger can be operated as a standard trigger if the set trigger is not pulled, or as a set trigger by first pulling the set trigger. Double set, double phase triggers offer the versatility of both a standard trigger and a set trigger. Pre-set strikers and hammers apply only to semi-automatic handguns. Upon firing a cartridge or loading the chamber, the hammer or striker will rest in a partially cocked position. The trigger serves the function of completing the cocking cycle and then releasing the striker or hammer. While technically two actions, it differs from a double-action trigger in that the trigger is not capable of fully cocking the striker or hammer. It differs from single action in that if the striker or hammer were to release, it would generally not be capable of igniting the primer. Examples of pre-set strikers are the Glock, Smith and Wesson M&P, Springfield Armory XDS (only), Kahr Arms, and Ruger SR series pistols. Examples of pre-set hammers are the Kel-Tec P-32 and Ruger LCP pistols. Pre-set hybrid triggers are similar to a DA/SA trigger in reverse. The first pull of the trigger is pre-set. If the striker or hammer fail to discharge the cartridge, the trigger may be pulled again and will operate as a double action only (DAO) until the cartridge discharges or the malfunction is cleared. This allows the operator to attempt to fire a cartridge after a misfire malfunction. The Taurus PT 24/7 Pro pistol (not to be confused with the first-generation 24/7 which was a traditional pre-set) offered this feature starting in 2006. The Walther P99 Anti-Stress is another example. Each trigger mechanism has its own merits. Historically, the first type of trigger was the single action. This is the simplest mechanism and generally the shortest, lightest, and smoothest pull available. The pull is also consistent from shot to shot so no adjustments in technique are needed for proper accuracy. On a single-action revolver, for which the hammer must be manually cocked prior to firing, an added level of safety is present. On a semi-automatic, the hammer will be cocked and made ready to fire by the process of chambering a round, and as a result an external safety is sometimes employed. Double action triggers provide the ability to fire the gun no matter whether the hammer is cocked or uncocked. This feature is desirable for military, police, or self-defense pistols. The primary disadvantage of any double-action trigger is the extra length the trigger must be pulled and the extra weight required to overcome the spring tension of the hammer or striker. DA/SA pistols are versatile mechanisms. These firearms generally have a manual safety that additionally may serve to decock the hammer. Some have a facility (generally a lever or button) to safely lower the hammer. As a disadvantage, these controls are often intermingled with other controls such as slide releases, magazine releases, take-down levers, takedown lever lock buttons, loaded chanber indicators, barrel tip-up levers, etc. These variables become confusing and require exponentially more complicated manuals-of-arms. One other disadvantage is the difference between the first double-action pull and subsequent single-action pulls. DAO firearms resolve some DA/SA shortcomings by making every shot a double-action shot. Because there is no difference in pull weights, training and practice are simplified. Additionally, negligent discharges are mitigated due to a heavier trigger pull. This is a particular advantage for a police pistol. These weapons also generally lack any type of external safety. DAO is common among police agencies and for small, personal protection firearms. The primary drawback is that additional trigger pull weight and travel required for each shot reduce accuracy. Pre-set triggers, only recently coming into vogue, offer a balance of pull weight, trigger travel, safety, and consistency. Glock popularized this trigger in modern pistols and many other manufacturers have released pre-set striker products of their own. The primary disadvantage is that pulling the trigger a second time after a failure to fire will not re-strike the primer. In normal handling of the firearm, this is not an issue; loading the gun requires that the slide be retracted, pre-setting the striker. Clearing a malfunction also usually involves retracting the slide following the "Tap rack bang" procedure. Many similar approaches are argued generally accomplishing the same end.

Muzzle brake
Muzzle brakes and recoil compensators are devices that are either fitted to, or designed as a permanent part of, the muzzle of a firearm or cannon to redirect propellant gases with the effect of countering both recoil of the gun and unwanted rising of the barrel during rapid fire. Muzzle brakes are useful for combat and timed competition shooting, and are commonly found on rifles firing large cartridges (such as big-game rifles), as well as some artillery and tank guns. They are also used on pistols for practical pistol competitions, and are usually called compensators in this context. The term muzzle brake was introduced in the context of artillery, but it is also used for rifles and pistols. It defines a device that reduces the recoil of the weapon by directing the propellant gases sideways and backwards. The force generated at the muzzle brake baffles or ejector ports acts in the opposite direction to the force of recoil, thus reducing wear on the recoil-damping mechanism and allowing a lighter design. In the case of smaller caliber firearms such as rifles it reduces the effects of kickback on the shooter. The terms recoil brake and recoil check are seldom used and never in artillery parlance. The terms recoil compensator, compensator, Mag-na-port and others belong to shooters' lingo and refer to devices that serve to direct propellant gases upwards to reduce muzzle climb and to some extent also the recoil in hand firearms like pistols and revolvers, and also in small-calibre automatic weapons like assault rifles, PDWs etc. With the exception of names for proprietary systems, such as Mag-na-porting and hybrid compensators, and brand names such as Muzzle Tamer, the various terms in the hand firearm parlance are used interchangeably. The interchangeable terms muzzle rise, muzzle flip, or muzzle climb refer to the tendency of a firearm's front end (the muzzle end of the barrel) to rise up after firing. The muzzle rises primarily because for most firearms, the centerline of the barrel is above the center of contact between the shooter and the firearms' grips and stock. The forces from the bullet being fired and the propellant gases exiting the muzzle act directly down the centerline of the barrel. If that line of force is above the center of the contact points, this creates a moment or torque rotational force, causing the firearm to rotate and the muzzle end to rise upwards. The M1946 Sieg automatic rifle had an unusual muzzle brake that made the rifle climb downwards, but enabled the user to fire it with one hand in full automatic. Firearms with less height from the grip line to the barrel centerline tend to experience less muzzle rise. Muzzle brakes are simple in concept, such as the 90 mm M3 gun which is used on the M47 Patton tank. This consists of a small length of tubing mounted at right angles to the end of the barrel. Brakes most often utilize slots, vents, holes, baffles, and similar devices. The strategy of a muzzle brake is to redirect and control the burst of combustion gases that follows the departure of a projectile. All muzzle brake designs share a basic principle: combustion gases are partly diverted at a generally sideways angle away from the muzzle end of the bore. The resulting change in the gases' momentum creates a reaction force which helps to counteract the rearward movement of the barrel due to recoil as well as the upward rise of the muzzle. The effect can be compared to the reverse thrust system on an aircraft jet engine. Another method of redirecting gases is called porting. Porting involves creating ports or holes that are precision-drilled into the forward part of the barrel (and slide on pistols and shotguns). These holes are designed to divert a portion of the gases expelled prior to the departure of the bullet in the direction that reduces the tendency of the firearm to flip upwards. The concept applies Newton's third law: the exhaust directed upward causes a reciprocal force downward. Porting is most commonly used on shotguns, where recoil is most significant and makes rapid firing difficult. Even single shots of magnum-strength loads are uncomfortable for all but the most seasoned shooters. Porting has obvious advantages for faster follow-up shots, especially for 3-round burst operation.][ Another strategy (besides redirecting gases) for counteracting muzzle rise involves slowing the departure of combustion gases. Slowing of the gases is the method used on suppressors and linear compensators. Construction of a muzzle brake or compensator can be as simple as a diagonal cut at the muzzle end of the barrel to direct some of the escaping gas upwards. On the AKM assault rifle, the brake is additionally angled slightly to the right to counteract the sideways movement of the rifle under recoil. Another simple method is porting, where holes or slots are machined in the barrel near the muzzle to allow the gas to escape. More advanced designs use baffles and expansion chambers to slow down the escaping gases; this is the basic principle behind a linear compensator. Ports are often added to the expansion chambers, producing the long, multi-chambered recoil compensators often seen on IPSC raceguns. There are advantages and disadvantages to muzzle brakes. Recoil may be perceived by different shooters as pain, movement of the sight line, rearward thrust, or some combination of the three. Recoil energy can be sharp if the impulse is fast or may be considered soft if the impulse is slower, even if the same total energy is transferred. Though there are numerous ways of measuring the energy of a recoil impulse, in general a 10% to 50% reduction can be measured. Some muzzle brake manufacturers claim greater recoil reduction percentages. Muzzle brakes need sufficient propellant gas volume and high gas pressure at the muzzle of the gun to achieve good measured recoil reduction percentages. This means cartridges with a large bore area to case volume ratio combined with a high operating pressure benefit more from recoil reduction with muzzle brakes than smaller standard cartridges. Besides reducing felt recoil, one of the primary advantages of a muzzle brake is the reduction of muzzle rise. This allows a weapon's sights to be realigned more quickly. This is relevant for fully automatic weapons. Muzzle rise is often eliminated][ by an efficient design. Because the rifle moves rearward less, the shooter has little to compensate for. Muzzle brakes benefit rapid-fire, fully automatic fire, and large-bore hunting rifles. They are also common on small-bore vermin rifles, where reducing the muzzle rise allows the shooter to see the bullet impact through a telescopic sight. A reduction in recoil also reduces the chance of undesired (painful) contacts between the shooter's head and the ocular of a telescopic sight or other aiming components that have to be positioned near the shooter's eye (often referred to as "scope eye"). Another advantage of a muzzle brake is a reduction of recoil fatigue during extended practice sessions, enabling the shooter to consecutively fire more rounds accurately. Further, flinch (involuntary pre-trigger-release anxiety behaviour resulting in inaccurate aiming and shooting) caused by excessive recoil may be reduced or eliminated with certain shooters. The advantages of brakes and compensators are not without downsides, however. The shooter, gun crew, or close bystanders may perceive an increase in sound pressure level as well as an increase in muzzle blast and lead exposure. This occurs because the sound, flash, pressure waves, and lead loaded smoke plume normally projected away from the shooter are now partially redirected outwards to the side or sometimes at partially backward angles towards the shooter or gun crew. Standard eye and ear protection, important for all shooters, may not be adequate to avoid hearing damage with the muzzle blast partially vectored back towards the gun crew or spotters by arrowhead shaped reactive muzzle brakes found on sniper team fired anti-materiel rifles like the Barrett M82. Measurements indicate that on a rifle a muzzle brake adds 5 to 10 dB to the normal noise level perceived by the shooter, increasing total noise levels up to 160 dB(A) +/- 3 dB. Painful discomfort occurs at approximately 120 to 125 dB(A), with some references claiming 133 dB(A) for the threshold of pain. Active ear muffs are available with electronic noise cancellation that can reduce direct path ear canal noise by approximately 17–33 dB, depending on the low, medium, or high frequency at which attenuation is measured. Passive ear plugs vary in their measured attenuation, ranging from 20 dB to 30 dB, depending on whether they are properly used. Using both ear muffs (whether passive or active) and ear plugs simultaneously results in maximum protection, but the efficacy of such combined protection relative to preventing permanent ear damage is inconclusive, with evidence indicating that a combined noise reduction ratio (NRR) of only 36 dB (C-weighted) is the maximum possible using ear muffs and ear plugs simultaneously, equating to only a 36 - 7 = 29 dB(A) protection against a 160 dB(A) noise level. Relative to a noise level of 160 dB(A), this means that even using ear muffs and ear plugs simultaneously cannot protect a shooter against permanent ear damage when using a muzzle brake, through leaving a shooter exposed to noise levels of approximately 131 dB(A) that is 11 dB above the point where permanent ear damage occurs. Brakes and compensators also add length, diameter, and mass to the muzzle end of a firearm, where it will most influence its handling. Brakes and compensators may interfere with accuracy. The problem is particularly pronounced when armour-piercing fin-stabilized discarding-sabot (APFSDS), a type of long-rod penetrator (LRP) are used.][ Since these APFSDS rounds are the most common armour-piercing ammunition currently, virtually no modern main battle tank guns have muzzle brakes. A serious tactical disadvantage of muzzle brakes on both small arms and artillery is that, depending on their designs, they may cause escaping gases to throw up dust and debris clouds that impair visibility and reveal one's position, not to mention posing a hazard to individuals without eye protection. Troops often wet the ground in front of antitank guns in defensive emplacements to prevent this, and snipers are specially trained in techniques for suppressing or concealing the magnified effects of lateral muzzle blast when firing rifles with such brakes.][ Linear compensators and suppressors do not have the disadvantages of a redirected muzzle blast; they actually reduce the blast by venting high pressure gas forward at reduced velocity. The redirection of larger amounts escaping high pressure gas can cause discomfort caused by blast-induced sinus cavity concussion. Such discomfort can especially become a problem for anti-materiel rifle shooters due to the bigger than normal cartridges with accompanying large case capacities and propellant volumes these rifles use and can be a reason for promoting accelerated shooter fatigue and flinching. Furthermore the redirected blast generates pressure waves inside the eyeball thus leading to retina ablation when intense battle shooting is performed with AM-guns and large calibers like .50 BMG. In some African jurisdictions where big game hunting is commonplace, rifles (typically firing powerful loads) equipped with muzzle brakes are banned due to hearing damage hazard to scouts and guides without hearing protection.

Gun barrel
A gun barrel is the tube, usually metal, through which a controlled explosion or rapid expansion of gases are released in order to propel a projectile out of the end at a high velocity. The first guns were made in a time where metallurgy was not advanced enough to cast tubes able to withstand the explosive forces of early cannon, so the pipe (often actually built from staves of metal) needed to be braced periodically along its length, producing an appearance somewhat reminiscent of a storage barrel. Another explanation, tied to etymology, states that many very first firearms barrels were in fact realized, during the 12th and 13th centuries, using small storage barrels with their usual metal rings reinforced by leather, hence the barrel name. In fact a set of old French words, some of them staying in modern French, were used as root words for various English terms related to firearms (and storage barrels). The old French gonne (pronounced by a French speaker it sounds approximately as gun does when pronounced by an English speaker) was a small barrel used on merchant and military ships. Likewise a baril was, as early as 1323 (used in Du Chevalier au barisel), and remains now, a big barrel. Moreover the big Tun English barrel is, as stated in Ton, the French old and contemporary tonne barrel. Modern day gun barrels are sophisticated in their construction and makeup. A gun barrel must be able to hold in the expanding gas produced by the propellants to ensure that optimum muzzle velocity is attained by the bullet or shell as it is being pushed out by the expanding gas(es). Early firearms were mostly muzzle loading (loaded from the mouth rather than the breech), which tends to be a slow and complicated procedure, resulting in a low rate of fire. Breech loading provided a higher rate of fire, but early breech loading guns lacked an effective way of sealing the escaping gases that leaked from the back end of the barrel; resulting in a lower muzzle velocity. During the 19th century, effective mechanical locks were invented that allowed loading from the breech while effectively sealing the breech from escaping propellant gases. Gun barrels are mostly of metal construction. The early Chinese, the inventors of gunpowder, used bamboo, a naturally tubular wood, as the first barrels in gunpowder projectile weapons.][ Early European guns were made of wrought iron, usually several bands of the metal arranged around circular wrought iron rings and then welded into a hollow cylinder. The Chinese were the first to master cast-iron cannon barrels. Bronze and brass were favoured by gunsmiths, due to their ease of casting and their ability to resist the corrosion created by the combustion of gunpowder. Early cannons were hugely thick for the caliber that they fired. Early manufacturing defects (such as air bubbles trapped in the metal) were key factors in many gun explosions, when the expanding gases became too much for the weak barrel, causing it to rupture and explode in deadly fragments. Generally the term "smallbore" refers firearms whose bore diameter is 0.299" or less. These are generally used for target shooting and hunting small game.

A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion or vice-versa. It is often a part of a rotating wheel (e.g. an eccentric wheel) or shaft (e.g. a cylinder with an irregular shape) that strikes a lever at one or more points on its circular path. The cam can be a simple tooth, as is used to deliver pulses of power to a steam hammer, for example, or an eccentric disc or other shape that produces a smooth reciprocating (back and forth) motion in the follower, which is a lever making contact with the cam. The cam can be seen as a device that rotates from circular to reciprocating (or sometimes oscillating) motion. A common example is the camshaft of an automobile, which takes the rotary motion of the engine and translates it into the reciprocating motion necessary to operate the intake and exhaust valves of the cylinders.
Certain cams can be characterized by their displacement diagrams, which reflect the changing position a roller follower (a shaft with a rotating wheel at the end) would make as the cam rotates about an axis. These diagrams relate angular position, usually in degrees, to the radial displacement experienced at that position. Displacement diagrams are traditionally presented as graphs with non-negative values. A simple displacement diagram illustrates the follower motion at a constant velocity rise followed by a similar return with a dwell in between as depicted in figure 2. The rise is the motion of the follower away from the cam center, dwell is the motion where the follower is at rest, and return is the motion of the follower toward the cam center. The most commonly used cam is the plate cam which is cut out of a piece of flat metal or plate. Here, the follower moves in a plane perpendicular to the axis of rotation of the camshaft. Several key terms are relevant in such a construction of plate cams: base circle, prime circle (with radius equal to the sum of the follower radius and the base circle radius), pitch curve which is the radial curve traced out by applying the radial displacements away from the prime circle across all angles, and the lobe separation angle (LSA - the angle between two adjacent intake and exhaust cam lobes). The base circle is the smallest circle that can be drawn to the cam profile. An early cam was built into Hellenistic water-driven automata from the 3rd century BC. The use of cams was later employed by Al-Jazari who employed them in his own automata. The cam and camshaft appeared in European mechanisms from the 14th century. Other mechanisms that convert between circular and reciprocating motion: Other mechanisms named "cam" or similar:

Firing pin
A firing pin or striker is part of the firing mechanism used in a firearm or explosive device e.g. an M14 landmine or bomb fuze. Firing pins may take many forms, though the types used in landmines, bombs, grenade fuzes or other single-use devices generally have a sharpened point. In contrast, firing pins used in firearms usually have a small, rounded portion designed to strike the primer of a cartridge, detonating the priming compound, which then ignites the propellant (in the case of firearms) or fires the detonator and booster. A firing pin is a lightweight part, which serves to transfer energy from a spring-loaded hammer to the primer, while a striker is usually heavier, and is directly connected to the spring providing the energy to impact the primer. Striker mechanisms are generally simpler, since they combine the functions of hammer and firing pin in one. The firing pin or striker is generally located in the bolt of a repeating firearm. Firearms that do not have bolts, such as revolvers and many types of single-shot actions, generally have a very short firing pin in the frame, or else attached to the hammer itself. These types of firearms are almost never striker fired, as there is insufficient space to house a striker mechanism. Strikers are most commonly found in semi-automatic pistols and bolt action firearms. The typical firing pin is a small rod of steel, with the end that strikes the primer rounded into a hemispherical shape and hardened. The rounded end ensures the primer is indented rather than pierced, as would happen if the firing pin were sharply pointed. Most firing pins have a spring to push them out of contact with the primer, and often will have an integrated passive safety mechanism, such as a block that prevents them from moving forward unless the trigger is depressed, or a transfer bar, also trigger actuated, that must be in place to allow the hammer to depress the firing pin. This safety is in addition to any manually operated safety or safeties that act to block the trigger or hammer. Firearms that use long firing pins, such as pistols, will often use a firing pin that is too short to project when depressed flush by the hammer. This type of firing pin, called an inertial firing pin, must be struck by a full fall of the hammer to provide the momentum to move forward and strike the primer. If the hammer is down, resting on the firing pin, it is very unlikely that a blow to the rear will provide enough energy to the firing pin to detonate the primer. Most variants of the M1911 pistol use this type of firing pin. Many firing pins are stamped from sheet steel, forming a rectangular cross-section rather than a round one. These will often have a cylindrical section at the front rather than a hemispherical one, and are fairly common in rimfire firearms. Sturm, Ruger, for example, uses sheet metal firing pins in its 10/22 carbine and Mark II pistol. High performance firing pins are often made from lighter materials than steel, such as titanium. The lighter material increases the speed at which the firing pin travels, and reduces the lock time, or the time from trigger pull to the bullet leaving the barrel. See accurize for more information. Strikers are basically spring-loaded firing pins, generally of a one- or two-piece construction. In the one-piece striker, the striker is turned on a lathe out of a round bar of metal, much larger in diameter than a firing pin, to provide the mass required to detonate the primer. Two-piece strikers generally consist of a firing pin attached to a heavier rear section—in essence a hammer attached to the base of a firing pin. Two-piece strikers are commonly found on bolt action rifles, while single-piece strikers are found on pistols, such as those made by Glock. Mechanisms involving firing pins can be used also in other pyrotechnical systems, ranging from hand grenades to chemical oxygen generators. Cutaway view of an M4 anti-tank mine showing integral firing pin Gyata-64 anti-personnel mine PM-79 antipersonnel mine Valmara 59 bounding mine MD-82 mine (Vietnamese near-copy of the M14 mine) Military boobytrap firing device from USSR (normally connected to a tripwire) showing integral striker. The detonator on the end is inserted into a block of explosive e.g. Semtex USSR booby trap firing device - pull fuze: normally connected to a tripwire USSR boobytrap firing device - pressure fuze: victim steps on loose floorboard with fuze concealed underneath.

Recoil (often called knockback, kickback or simply kick) is the backward momentum of a gun when it is discharged. In technical terms, the recoil caused by the gun exactly balances the forward momentum of the projectile and exhaust gasses (ejecta), according to Newton's third law. In most small arms, the momentum is transferred to the ground through the body of the shooter; while in heavier guns such as mounted machine guns or cannons, the momentum is transferred to the ground through its mount. In order to bring the gun to a halt, a forward counter-recoil force must be applied to the gun over a period of time. Generally, the counter-recoil force is smaller than the recoil force, and is applied over a time period that is longer than the time that the recoil force is being applied (i.e. the time during which the ejecta are still in the barrel of the gun). This imbalance of forces causes the gun to move backward until it is motionless. A change in momentum results in a force, which according to Newton's second law is equal to the time derivative of the momentum of the gun. The momentum is equal to the mass of the gun multiplied by its velocity. This backward momentum is equal in magnitude, by the law of conservation of momentum, to the forward momentum of the ejecta (projectile(s), wad, propellant gases, etc...) from the gun. If the mass and velocity of the ejecta are known, it is possible to calculate a gun’s momentum and thus the energy. In practice, it is often simpler to derive the gun’s energy directly with a reading from a ballistic pendulum or ballistic chronograph. There are two conservation laws at work when a gun is fired: conservation of momentum and conservation of energy. Recoil is explained by the law of conservation of momentum, and so it is easier to discuss it separately from energy. The nature of the recoil process is determined by the force of the expanding gases in the barrel upon the gun (recoil force), which is equal and opposite to the force upon the ejecta. It is also determined by the counter-recoil force applied to the gun (e.g. an operators hand or shoulder, or a mount, in the case of a mounted gun). The recoil force only acts during the time that the ejecta are still in the barrel of the gun. The counter-recoil force is generally applied over a certain time period and adds forward momentum to the gun equal to the backward momentum supplied by the recoil force, in order to bring the gun to a halt. There are two special cases of counter recoil force: Free-recoil, in which the time duration of the counter-recoil force is very much larger than the duration of the recoil force, and zero-recoil, in which the counter-recoil force matches the recoil force in magnitude and duration. Except for the case of zero-recoil, the counter-recoil force is smaller than the recoil force but lasts for a longer time. Since the recoil force and the counter-recoil force are not matched, the gun will move rearward, slowing down until it comes to rest. In the zero-recoil case, the two forces are matched and the gun will not move when fired. In most cases, a gun is very close to a free-recoil condition, since the recoil process generally lasts much longer than the time needed to move the ejecta down the barrel. An example of near zero-recoil would be a gun securely clamped to a massive or well-anchored table, or supported from behind by a massive wall. The recoil of a firearm, whether large or small, is a result of the law of conservation of momentum. Assuming that the firearm and projectile are both at rest before firing, then their total momentum is zero. Assuming a near free-recoil condition, and neglecting the gases ejected from the barrel, then immediately after firing, conservation of momentum requires that the total momentum of the firearm and projectile is the same as before, namely zero. Stating this mathematically: where p_f\, is the momentum of the firearm and p_p\, is the momentum of the projectile. In other words, immediately after firing, the momentum of the firearm is equal and opposite to the momentum of the projectile. Since momentum of a body is defined as its mass multiplied by its velocity, we can rewrite the above equation as: where: A force integrated over the time period during which it acts will yield the momentum supplied by that force. The counter-recoil force must supply enough momentum to the firearm to bring it to a halt. This means that: where: A similar equation can be written for the recoil force on the firearm: where: Assuming the forces are somewhat evenly spread out over their respective durations, the condition for free-recoil is t_r \ll t_f, while for zero-recoil, F_r(t)+F_{cr}(t)=0. For a gun firing under free-recoil conditions, the force on the gun will not only force the gun backwards, but will also cause it to rotate about its center of mass. The torque (\tau) on the gun is given by: where h is the perpendicular distance of the center of mass of the gun below the barrel axis, F(t) is the force on the gun due to the expanding gases, equal and opposite to the force on the bullet, I is the moment of inertia of the gun about its center of mass, and \theta is the angle of rotation of the barrel axis "up" from its orientation at ignition (aim angle). The angular momentum of the gun is found by integrating this equation to obtain: where the equality of the momenta of the gun and bullet have been used. The angular rotation of the gun as the bullet exits the barrel is then found by integrating again: where \theta_f is the angle above the aim angle at which the bullet leaves the barrel, t_f is the time of travel of the bullet in the barrel and L is the distance the bullet travels from its rest position to the tip of the barrel. The angle at which the bullet leaves the barrel above the aim angle is then given by: The momentum of the ejected gases will not contribute very much to this result, since much of the ejected gases exit the barrel after the bullet has left the barrel. A consideration of energy leads to a different equation. From Newton's second law, the energy of a moving body due to its motion can be stated mathematically from the translational kinetic energy as: where: This equation is known as the "classic statement" and yields a measurement of energy in joules (or foot-pound force in non-SI units). E_t\, is the amount of work that can be done by the recoiling firearm, firearm system, or projectile because of its motion, and is also called the translational kinetic energy. In the firearms lexicon, the energy of a recoiling firearm is called felt recoil, free recoil, and recoil energy. This same energy from a projectile in motion is called: muzzle energy, bullet energy, remaining energy. The energy of the projectile at the point of impact is known as the down range energy or impact energy and generally will be slightly smaller than the muzzle energy due to wind resistance acting upon the projectile. Again assuming free-recoil conditions and assuming all forward momentum is due to the projectile, the energy of the projectile will be E_p=p_p^2/2m_p and the energy of the firearm due to recoil will be E_f=p_f^2/2m_f. Since, by Newton's third law, p_f+p_p=0, it follows that the ratios of the energies is given by: The mass of the firearm (m_f) is generally much greater than the projectile mass (m_p) which means that most of the kinetic energy produced by the firing of the firearm is given to the projectile. For example, a rifle weighing 5 pounds firing a 150 grain bullet, the recoil energy will be only 0.43 percent of the total kinetic energy developed. In the case of zero-recoil, the firearm will gain no energy, and the energy of the projectile will be increased by 0.43 percent over that of the free-recoil case. The recoil energy is generally absorbed by the mechanism which produces the counter-recoil force, and is dissipated as heat. For a hand-held firearm, the energy is absorbed by the shooter's body, creating a small amount of heat. For the naval cannon from the figure above, it will roll backwards and the recoil energy will be mostly absorbed by the friction forces in the wheel axles and between the wheel and the ship deck and this energy is again converted to heat. The backward momentum applied to the firearm is actually equal and opposite to the momentum of not only the projectile, but the ejected gas created by the combustion of the charge as well. Likewise, the recoil energy given to the firearm is affected by the ejected gas. By conservation of mass, the mass of the ejected gas will be equal to the original mass of the propellant. As a rough approximation, the ejected gas can be considered to have an effective exit velocity of \alpha V_0 where V_0 is the muzzle velocity of the projectile and \alpha is approximately constant. The total momentum p_e of the propellant and projectile will then be: where: m_g\, is the mass of the propellant charge, equal to the mass of the ejected gas. This expression should be substituted into the expression for projectile momentum in order to obtain more a more accurate description of the recoil process. The effective velocity may be used in the energy equation as well, but since the value of α used is generally specified for the momentum equation, the energy values obtained may be less accurate. The value of the constant α is generally taken to lie between 1.25 and 1.75. It is mostly dependent upon the type of propellant used, but may depend slightly on other things such as the ratio of the length of the barrel to its radius. For small arms, the way in which the shooter perceives the recoil, or kick, can have a significant impact on the shooter's experience and performance. For example, a gun that is said to "kick like a mule" is going to be approached with trepidation, and the shooter will anticipate the recoil and flinch in anticipation as the shot is released. This leads to the shooter jerking the trigger, rather than pulling it smoothly, and the jerking motion is almost certain to disturb the alignment of the gun and result in a miss. This perception of recoil is related to the acceleration associated with a particular gun. The actual recoil is associated with the momentum of a gun, the momentum being the product of the mass of the gun times the reverse velocity of the gun. A heavier gun, that is a gun with more mass, will manifest the momentum by exhibiting a lessened acceleration, and, generally, result in a lessened perception of recoil. One of the common ways of describing the felt recoil of a particular gun-cartridge combination is as "soft" or "sharp" recoiling; soft recoil is recoil spread over a longer period of time, that is at a lower acceleration, and sharp recoil is spread over a shorter period of time, that is with a higher acceleration. With the same gun and two loads with different bullet masses but the same recoil force, the load firing the heavier bullet will have the softer recoil, because the product of mass times acceleration must remain constant, and if mass goes up then acceleration must go down, to keep the product constant. Keeping the above in mind, you can generally base the relative recoil of firearms by factoring in a number of figures such as bullet weight, powder charge, the weight of the actual firearm etc. The following are base examples calculated through the free online calculator, and bullet and firearm data from respective reloading manuals (of medium/common loads) and manufacturer specs: In addition to the overall mass of the gun, reciprocating parts of the gun will affect how the shooter perceives recoil. While these parts are not part of the ejecta, and do not alter the overall momentum of the system, they do involve moving masses during the operation of firing. For example, gas-operated shotguns are widely held to have a "softer" recoil than fixed breech or recoil-operated guns. In a gas-operated gun, the bolt is accelerated rearwards by propellant gases during firing, which results in a forward force on the body of the gun. This is countered by a rearward force as the bolt reaches the limit of travel and moves forwards, resulting in a zero sum, but to the shooter, the recoil has been spread out over a longer period of time, resulting in the "softer" feel. A recoil system absorbs recoil energy, reducing the peak force that is conveyed to whatever the gun is mounted on. Old-fashioned cannons without a recoil system roll several meters backwards when fired. First was introduced in Russia as Baranovsky gun pl:Oporopowrotnik by Wladimir Baranovsky ru:Барановский, Владимир Степанович in 1872 (short recoil operation) and later in France (based on Baranovsky construction) - 75mm field gun of 1897 (long recoil operation). The usual recoil system in modern quick-firing guns is the hydro-pneumatic recoil system. In this system, the barrel is mounted on rails on which it can recoil to the rear, and the recoil is taken up by a cylinder which is similar in operation to an automotive gas-charged shock absorber, and is commonly visible as a cylinder mounted parallel to the barrel of the gun, but shorter and smaller than it. The cylinder contains a charge of compressed air, as well as hydraulic oil; in operation, the barrel's energy is taken up in compressing the air as the barrel recoils backward, then is dissipated via hydraulic damping as the barrel returns forward to the firing position. The recoil impulse is thus spread out over the time in which the barrel is compressing the air, rather than over the much narrower interval of time when the projectile is being fired. This greatly reduces the peak force conveyed to the mount (or to the ground on which the gun has been emplaced). In a soft-recoil system, the spring (or air cylinder) that returns the barrel to the forward position starts out in a nearly fully compressed position, then the gun's barrel is released free to fly forward in the moment before firing; the charge is then ignited just as the barrel reaches the fully forward position. Since the barrel is still moving forward][ when the charge is ignited, about half of the recoil impulse is applied to stopping the forward motion of the barrel, while the other half is, as in the usual system, taken up in recompressing the spring. A latch then catches the barrel and holds it in the starting position. This roughly halves the energy that the spring needs to absorb, and also roughly halves the peak force conveyed to the mount, as compared to the usual system. However, the need to reliably achieve ignition at a single precise instant is a major practical difficulty with this system; and unlike the usual hydro-pneumatic system, soft-recoil systems do not easily deal with hangfires or misfires. One of the early guns to use this system was the French 65 mm mle.1906; it was also used by the World War II British PIAT man-portable anti-tank weapon. Recoilless rifles and rocket launchers exhaust gas to the rear, balancing the recoil. They are used often as light anti-tank weapons. The Swedish-made Carl Gustav 84mm recoilless gun is such a weapon. In machine guns following Hiram Maxim's design - e.g. the Vickers machine gun - the recoil of the barrel is used to drive the feed mechanism. Hollywood depictions of firearm shooting victims being thrown through several feet backwards are inaccurate, although not for the often-cited reason of conservation of energy. Although energy must be conserved, this does not mean that the kinetic energy of the bullet must be equal to the recoil energy of the gun: in fact, it is many times greater. For example, a bullet fired from an M16 rifle has approximately 1763 Joules of kinetic energy as it leaves the muzzle, but the recoil energy of the gun is less than 7 Joules. Despite this imbalance, energy is still conserved because the total energy in the system before firing (the chemical energy stored in the propellant) is equal to the total energy after firing (the kinetic energy of the recoiling firearm, plus the kinetic energy of the bullet and other ejecta, plus the heat energy from the explosion). In order to work out the distribution of kinetic energy between the firearm and the bullet, it is necessary to use the law of conservation of momentum in combination with the law of conservation of energy. The same reasoning applies when the bullet strikes a target. The bullet may have a kinetic energy in the hundreds or even thousands of joules, which in theory is enough to lift a person well off the ground. This energy, however, cannot be efficiently given to the target, because total momentum must be conserved, too. Approximately, only a fraction not larger than the inverse ratio of the masses can be transferred. The rest is spent in the deformation or shattering of the bullet (depending on bullet construction), damage to the target (depending on target construction), and heat dissipation. In other words, because the bullet strike on the target is an inelastic collision, a minority of the bullet energy is used to actually impart momentum to the target. This is why a ballistic pendulum relies on conservation of bullet momentum and pendulum energy rather than conservation of bullet energy to determine bullet velocity; a bullet fired into a hanging block of wood or other material will spend much of its kinetic energy to create a hole in the wood and dissipate heat as friction as it slows to a stop. Gunshot victims frequently do collapse when shot, which is usually due to psychological motives, a direct hit to the central nervous system, and/or massive blood loss (see stopping power), and is not the result of the momentum of the bullet pushing them over.

Chrome plating
Chrome plating (less commonly chromium plating), often referred to simply as chrome, is a technique of electroplating a thin layer of chromium onto a metal or plastic object. The chromed layer can be decorative, provide corrosion resistance, ease cleaning procedures, or increase surface hardness, and sometimes for aesthetic purposes a less expensive imitator of chrome will be used. A component to be chrome plated will generally go through these different stages: There are many variations to this process depending on the type of substrate being plated upon. Different etching solutions are used for different substrates. Hydrochloric, hydrofluoric, and sulfuric acids can be used. Ferric chloride is also popular for the etching of Nimonic alloys. Sometimes the component will enter the chrome plating vat electrically live. Sometimes the component will have a conforming anode either made from lead/tin or platinized titanium. A typical hard chrome vat will plate at about 1 mil (25 µm) per hour. Various linishing and buffing processes are used in preparing components for decorative chrome plating. The overall appearance of decorative chrome plating is only as good as the preparation of the component. The chrome plating chemicals are very toxic. Disposal of chemicals is regulated in most countries. Hexavalent chromium plating, also known as hex-chrome, Cr+6, and chrome (VI) plating, uses chromic anhydride, also known as chromium trioxide, as the main ingredient. Hexavalent chromium plating solution is used for decorative and hard plating, along with bright dipping of copper alloys, chromic acid anodizing, and chromate conversion coating. A typical hexavalent chromium plating process is: (1) activation bath, (2) chromium bath, (3) rinse, and (4) rinse. The activation bath is typically a tank of chromic acid with a reverse current run through it; this etches the workpiece surface and removes any scale. In some cases the activation step is done in the chromium bath. The chromium bath is a mixture of chromium trioxide (CrO3) and sulfuric acid (sulfate, SO4); the ratio of which varies greatly between 75:1 to 250:1 by weight. This results in an extremely acidic bath (pH 0). The temperature and current density in the bath affect the brightness and final coverage. For decorative coating the temperature ranges from 95 to 115 °F (35 to 46 °C), but for hard coating it ranges from 120 to 150 °F (49 to 66 °C). Temperature is also dependent on the current density, because a higher current density requires a higher temperature. Finally, the whole bath is agitated to keep temperature steady and increase a uniform deposition. One functional disadvantage of hexavalent chromium plating is low cathode efficiency, which results in bad throwing power. This means it leaves a non-uniform coating, with more on edges and less in inside corners and holes. To overcome this problem the part may be over-plated and ground to size, or auxiliary anodes are used around the hard-to-plate areas. From a health standpoint, hexavalent chromium is the most toxic form of chromium. In the U.S. it is heavily regulated by the Environmental Protection Agency (EPA); the EPA lists it as a hazardous air pollutant because it is a human carcinogen, a "priority pollutant" under the Clean Water Act, and a "hazardous constituent" under the Resource Conservation and Recovery Act. Due to the low cathodic efficiency and high solution viscosity a mist of water and hexavalent chromium is released from the bath, which is toxic. To control these emissions wet scrubbers are used. The discharge from the wet scrubbers is then treated to precipitate the chromium from the solution, because it cannot be discarded in the waste water. Maintaining a bath surface tension less than 35 dynes/cm requires frequent cycle of treating the bath by a wetting agent and confirming the effect on surface tension. Traditionally surface tension is measured by a stalagmometer. This method is, however, tedious and suffers from inaccuracy (errors up 22 dynes/cm has been reported), and is dependent on user's experience and capabilities. Additional toxic waste that is created from hexavalent chromium baths include lead chromates which form in the bath because lead anodes are used. Barium is also used to control the sulfate concentration, which leads to the formation of barium sulfate, a hazardous waste. Trivalent chromium plating, also known as tri-chrome, Cr+3, and chrome (III) plating, uses chromium sulfate or chromium chloride as the main ingredient. Trivalent chromium plating is an alternative to hexavalent chromium in certain applications and thicknesses (e.g. decorative plating). A trivalent chromium plating process is similar to the hexavalent chromium plating process except for the bath chemistry and anode composition. There are three main types of trivalent chromium bath configurations: The trivalent chromium plating process plates workpieces at a similar temperature, rate and hardness, as compared to hexavalent chromium. Plating thickness range from 0.005 to 0.05 mils (0.13 to 1.3 µm). The functional advantages of trivalent chromium are higher cathode efficiency and better throwing power. The better throwing power means production rates are greater. Less energy is required because of the lower current densities required. The process is more robust than hexavalent chromium because it can withstand current interruptions. From a health standpoint trivalent chromium is intrinsically less toxic than hexavalent chromium. Because of the lower toxicity it is not regulated as strictly, which reduces overhead costs. There are other secondary health advantages: One of the disadvantages when the process was first introduced was that decorative customers disapproved of the color differences, however additives are now used to adjust the color. In hard coating applications, the corrosion resistance of thicker coatings is not quite as good as hexavalent chromium. The cost of the chemicals is greater, however this is usually offset by greater production rates and lower overhead costs. In general, the process must be controlled more closely than in hexavalent chromium plating, especially with respect to metallic impurities. This means processes that are hard to control, such as barrel plating, are much more difficult using a trivalent chromium bath. is designed to be aesthetically pleasing and durable. Thicknesses range from 0.002 to 0.02 mils (0.05 to 0.5 µm), however they are usually between 0.005 and 0.01 mils (0.13 and 0.25 µm). The chromium plating is usually applied over bright nickel plating. Typical base materials include steel, aluminum, plastic, copper alloys, and zinc alloys. , also known as or , is used to reduce friction, improve durability through abrasion tolerance and wear resistance in general, minimize galling or seizing of parts, expand chemical inertness to include a broader set of conditions, especially oxidation resistance which is arguably its most famous quality, and bulking material for worn parts to restore their original dimensions. It is very hard, measuring between 65 to 69 HRC. Hard chrome tends to be thicker than the decorative treatment, with standard thicknesses in nonsalvage applications ranging from 0.2 to 0.6 mils (5 to 15 µm), but can be an order of magnitude thicker for extreme wear resistance requirements, in such cases 1 mil (25 µm) or thicker should be used for optimal results. Unfortunately, such thicknesses emphasize the limitations of the process, which are overcome by plating extra thickness then grinding down and lapping to meet requirements or to improve overall aesthetics of the "chromed" piece. With increased plating thickness, surface defects and roughness are amplified in proportional severity, because hard chrome does not have a leveling effect and pieces which are not ideally shaped in reference to electric field geometries (i.e. nearly every piece sent in for plating, except spheres and egg shaped objects) will require even thicker plating to compensate for non-uniform deposition, and much of it is wasted when grinding back to desired dimensions. Modern "engineered coatings" do not suffer such drawbacks, which often price hard chrome out due to labor costs alone. Hard chrome replacement technologies outperform hard chrome in wear resistance, corrosion resistance, and cost. Rockwell hardness 80 is not extraordinary for such materials. By using spray deposition, uniform thickness which often requires no further polishing or machining is a standard feature of modern engineered coatings—which are often composites of polymers, metals, and ceramic powders or fibers as proprietary embodiments protected by patents or as trade secrets, and thus are usually known by brand names. Hard chromium plating is subject to different types of quality requirements depending on the application, for instance, the plating on hydraulic piston rods are tested for corrosion resistance with a salt spray test. Formerly most decorative items affixed to cars were referred to as "chrome", by which phrase was actually meant steel that had undergone several plating processes to endure the temperature changes and weather that a car was subject to outdoors. The most expensive and durable process involved plating the steel first with copper, and then nickel, before the chromium plating was applied. Prior to the application of chrome in the 1920s, nickel electroplating was used. In the US for the short production run prior to the entry into the Second World War, plating was banned to save chromium and the decorative pieces were painted in a complementary color. In the last years of the Korean War, the banning of chrome was contemplated and several cheaper processes (such as plating with zinc and then coating with shiny plastic) were considered. In 2007, a Restriction of Hazardous Substances Directive (RoHS) was issued banning several toxic substances for use in the automotive industry in Europe, including hexavalent chromium, which is used in chrome plating. However, chrome plating is metal and contains no hexavalent chromium after it is rinsed, so chrome plating is not banned.
metal plate
Striking clock

A striking clock is a clock that sounds the hours audibly on a bell or gong. In 12 hour striking, used most commonly in striking clocks today, the clock strikes once at one a.m., twice at two a.m., continuing in this way up to twelve times at 12 noon, then starts again, striking once at one p.m., twice at two p.m., up to twelve times at 12 midnight.

The striking feature of clocks was originally more important than their clock faces; the earliest clocks struck the hours, but had no dials to enable the time to be read. The development of mechanical clocks in Europe was motivated by the need to ring bells upon the canonical hours to call the community to prayer. The earliest known mechanical clocks were large striking clocks installed in towers in monasteries or public squares, so that their bells could be heard far away. Though an early striking clock in Syria was a 12 hour clock, many early clocks struck up to 24 strokes, particularly in Italy, where the 24 hour clock, keeping Italian hours, was widely used in the 14th and 15th centuries. As the modern 12 hour clock became more widespread, particularly in Great Britain and Northern Europe, 12 hour striking became more widespread and eventually became the standard.

Time Measurement Clocks Horology

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