Suppressor
Overview
 
A suppressor, sound suppressor, sound moderator, or silencer, is a device attached to or part of the barrel
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....

 of a firearm
Firearm
A firearm is a weapon that launches one, or many, projectile at high velocity through confined burning of a propellant. This subsonic burning process is technically known as deflagration, as opposed to supersonic combustion known as a detonation. In older firearms, the propellant was typically...

 which reduces the amount of noise
Noise
In common use, the word noise means any unwanted sound. In both analog and digital electronics, noise is random unwanted perturbation to a wanted signal; it is called noise as a generalisation of the acoustic noise heard when listening to a weak radio transmission with significant electrical noise...

 and flash
Muzzle flash
Muzzle blast is the term used to describe the release of high temperature, high pressure gases expelled from the muzzle of a firearm when it is discharged. Muzzle flash is the term used to describe the visible light of the muzzle blast. The blast and flash are caused by the combustion products of...

 generated by firing the weapon.

A suppressor is usually a metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...

 cylinder
Cylinder (geometry)
A cylinder is one of the most basic curvilinear geometric shapes, the surface formed by the points at a fixed distance from a given line segment, the axis of the cylinder. The solid enclosed by this surface and by two planes perpendicular to the axis is also called a cylinder...

 with internal mechanisms to reduce the sound of firing by slowing the escaping propellant
Propellant
A propellant is a material that produces pressurized gas that:* can be directed through a nozzle, thereby producing thrust ;...

 gas and sometimes by reducing the velocity of the bullet
Bullet
A bullet is a projectile propelled by a firearm, sling, or air gun. Bullets do not normally contain explosives, but damage the intended target by impact and penetration...

.

Early suppressors were created around the beginning of the 20th century by several inventors.
Encyclopedia
A suppressor, sound suppressor, sound moderator, or silencer, is a device attached to or part of the barrel
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....

 of a firearm
Firearm
A firearm is a weapon that launches one, or many, projectile at high velocity through confined burning of a propellant. This subsonic burning process is technically known as deflagration, as opposed to supersonic combustion known as a detonation. In older firearms, the propellant was typically...

 which reduces the amount of noise
Noise
In common use, the word noise means any unwanted sound. In both analog and digital electronics, noise is random unwanted perturbation to a wanted signal; it is called noise as a generalisation of the acoustic noise heard when listening to a weak radio transmission with significant electrical noise...

 and flash
Muzzle flash
Muzzle blast is the term used to describe the release of high temperature, high pressure gases expelled from the muzzle of a firearm when it is discharged. Muzzle flash is the term used to describe the visible light of the muzzle blast. The blast and flash are caused by the combustion products of...

 generated by firing the weapon.

A suppressor is usually a metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...

 cylinder
Cylinder (geometry)
A cylinder is one of the most basic curvilinear geometric shapes, the surface formed by the points at a fixed distance from a given line segment, the axis of the cylinder. The solid enclosed by this surface and by two planes perpendicular to the axis is also called a cylinder...

 with internal mechanisms to reduce the sound of firing by slowing the escaping propellant
Propellant
A propellant is a material that produces pressurized gas that:* can be directed through a nozzle, thereby producing thrust ;...

 gas and sometimes by reducing the velocity of the bullet
Bullet
A bullet is a projectile propelled by a firearm, sling, or air gun. Bullets do not normally contain explosives, but damage the intended target by impact and penetration...

.

Early suppressors were created around the beginning of the 20th century by several inventors. American
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 inventor Hiram Percy Maxim
Hiram Percy Maxim
Hiram Percy Maxim was an American radio pioneer and inventor, and co-founder of the American Radio Relay League . He originally had the amateur call signs SNY, 1WH, 1ZM, 1AW, and later W1AW, which is now the ARRL Headquarters club station call sign...

 (not to be confused with Hiram Stevens Maxim, inventor of the Maxim Machine Gun), is credited with inventing and selling the first commercially successful models circa 1902 (Patented 24th May 1910 ). Maxim gave his device the trademarked name Maxim Silencer. The muffler
Muffler
A muffler is a device for reducing the amount of noise emitted by the exhaust of an internal combustion engine. A US Patent for an Exhaust muffler for engines was granted to Milton and Marshall Reeves in 1897....

 for internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

s was developed in parallel with the firearm suppressor by Maxim in the early 20th century, using many of the same techniques to provide quieter-running engines. Indeed, in many European countries, automobile mufflers are still referred to as "silencers". The proper name Silencer has since fallen out of favor with some among the firearms industry, being replaced with the more literally accurate term sound suppressor or just suppressor, because a "sound suppressor" does not "silence" any weapon, rather it eliminates muzzle flash and reduces the sonic pressure of a firearm discharging. Common usage and U.S. legislative language favor the historically earlier term, silencer. In U.S. law, the terms "firearm muffler" and "firearm silencer" are synonymous.

Suppressors were regularly used by agents of the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 Office of Strategic Services
Office of Strategic Services
The Office of Strategic Services was a United States intelligence agency formed during World War II. It was the wartime intelligence agency, and it was a predecessor of the Central Intelligence Agency...

, who favored the newly designed High Standard HDM .22 Long Rifle
.22 Long Rifle
The .22 Long Rifle rimfire cartridge is a long established variety of ammunition, and in terms of units sold is still by far the most common in the world today. The cartridge is often referred to simply as .22 LR and various rifles, pistols, revolvers, and even some smoothbore shotguns have...

 pistol during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. OSS Director William Joseph "Wild Bill" Donovan
William Joseph Donovan
William Joseph Donovan was a United States soldier, lawyer and intelligence officer, best remembered as the wartime head of the Office of Strategic Services...

 demonstrated the pistol for President
President of the United States
The President of the United States of America is the head of state and head of government of the United States. The president leads the executive branch of the federal government and is the commander-in-chief of the United States Armed Forces....

 Franklin D. Roosevelt
Franklin D. Roosevelt
Franklin Delano Roosevelt , also known by his initials, FDR, was the 32nd President of the United States and a central figure in world events during the mid-20th century, leading the United States during a time of worldwide economic crisis and world war...

 at the White House
White House
The White House is the official residence and principal workplace of the president of the United States. Located at 1600 Pennsylvania Avenue NW in Washington, D.C., the house was designed by Irish-born James Hoban, and built between 1792 and 1800 of white-painted Aquia sandstone in the Neoclassical...

. According to OSS research chief Stanley Lovell, Donovan (an old and trusted friend of the President) was waved into the Oval Office
Oval Office
The Oval Office, located in the West Wing of the White House, is the official office of the President of the United States.The room features three large south-facing windows behind the president's desk, and a fireplace at the north end...

, where Roosevelt was dictating a letter. While Roosevelt finished his message, Donovan turned his back and fired ten shots into a sandbag he had brought with him, announced what he had done and handed the smoking gun to the astonished president.

Design and construction

The suppressor is typically a hollow cylindrical piece of machined metal (steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

, aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

, or titanium
Titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....

) containing expansion chambers that attaches to the muzzle
Muzzle (firearm)
The muzzle of a firearm is the end of the barrel from which the projectile will exit.Precise machining of the muzzle is crucial to accuracy, because it is the last point of contact between the barrel and the projectile...

 of a pistol
Pistol
When distinguished as a subset of handguns, a pistol is a handgun with a chamber that is integral with the barrel, as opposed to a revolver, wherein the chamber is separate from the barrel as a revolving cylinder. Typically, pistols have an effective range of about 100 feet.-History:The pistol...

, submachine gun
Submachine gun
A submachine gun is an automatic carbine, designed to fire pistol cartridges. It combines the automatic fire of a machine gun with the cartridge of a pistol. The submachine gun was invented during World War I , but the apex of its use was during World War II when millions of the weapon type were...

 or rifle
Rifle
A rifle is a firearm designed to be fired from the shoulder, with a barrel that has a helical groove or pattern of grooves cut into the barrel walls. The raised areas of the rifling are called "lands," which make contact with the projectile , imparting spin around an axis corresponding to the...

. These "can"-type suppressors (so-called as they resemble a beverage can
Beverage can
A beverage can is a tin can designed to hold a specific portion of a beverage. Beverage cans are made of tin-plated steel or aluminium.- History :...

), may be detached by the user and attached to a different firearm of the same caliber
Caliber
In guns including firearms, caliber or calibre is the approximate internal diameter of the barrel in relation to the diameter of the projectile used in it....

. Another type is the "integral" suppressor, which consists of expansion chambers surrounding the barrel. The barrel is pierced with openings or "ports" which bleed off gases into the chambers. This type of suppressor is part of the firearm, and maintenance of the suppressor requires that the firearm be at least partially disassembled.

Both types of suppressor reduce noise by allowing the rapidly expanding gases from the firing of the cartridge to be briefly diverted or trapped inside a series of hollow chambers. The trapped gas expands and cools, and its pressure and velocity decreases as it exits the suppressor. The chambers are divided by either baffles
Sound baffle
A sound baffle is a construction or device which reduces the strength of airborne sound. Sound baffles are a fundamental tool of noise mitigation, the practice of minimizing noise pollution or reverberation. An important type of sound baffle is the noise barrier constructed along highways to...

or wipes (see below). There are typically at least four and up to perhaps fifteen chambers in a suppressor, depending on the intended use and design details. Often, a single, larger expansion chamber is located at the muzzle end of a can-type suppressor, which allows the propellant gas to expand considerably and slow down before it encounters the baffles or wipes. This larger chamber may be "reflexed" toward the rear of the barrel to minimize the overall length of the combined firearm and suppressor, especially with longer weapons such as rifles.

Suppressors vary greatly in size and efficiency. One disposable type developed in the 1980s by the U.S. Navy for 9 mm pistols was 150 mm (5.9 in) long and 45 mm (1.8 in) in outside diameter, and was designed for six shots with standard ammunition or up to thirty shots with subsonic
Speed of sound
The speed of sound is the distance travelled during a unit of time by a sound wave propagating through an elastic medium. In dry air at , the speed of sound is . This is , or about one kilometer in three seconds or approximately one mile in five seconds....

 (slower than the speed of sound) ammunition
Ammunition
Ammunition is a generic term derived from the French language la munition which embraced all material used for war , but which in time came to refer specifically to gunpowder and artillery. The collective term for all types of ammunition is munitions...

. In contrast, one suppressor designed for rifles firing the powerful .50 caliber
.50 BMG
The .50 Browning Machine Gun or 12.7×99mm NATO is a cartridge developed for the Browning .50 caliber machine gun in the late 1910s. Entering service officially in 1921, the round is based on a greatly scaled-up .30-06 cartridge...

 cartridge is 509 mm (20 in) long and 76 mm (3 in) in diameter.

Components

Baffles
Sound baffle
A sound baffle is a construction or device which reduces the strength of airborne sound. Sound baffles are a fundamental tool of noise mitigation, the practice of minimizing noise pollution or reverberation. An important type of sound baffle is the noise barrier constructed along highways to...

 are usually circular metal dividers which separate the expansion chambers. Each baffle has a hole in its center to permit the passage of the bullet through the suppressor and towards the target. The hole is typically at least 0.04 inch (1 mm) larger than the bullet caliber to minimize the risk of the bullet hitting the baffle ("baffle strike"). Baffles are typically made of stainless steel
Stainless steel
In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass....

, aluminium, titanium or alloys such as Inconel
Inconel
Inconel is a registered trademark of Special Metals Corporation that refers to a family of austenitic nickel-chromium-based superalloys. Inconel alloys are typically used in high temperature applications. It is often referred to in English as "Inco"...

, and are either machined
Machining
Conventional machining is a form of subtractive manufacturing, in which a collection of material-working processes utilizing power-driven machine tools, such as saws, lathes, milling machines, and drill presses, are used with a sharp cutting tool to physical remove material to achieve a desired...

 out of solid metal or stamped
Stamping (metalworking)
Stamping includes a variety of sheet-metal forming manufacturing processes, such as punching using a machine press or stamping press, blanking, embossing, bending, flanging, and coining. This could be a single stage operation where every stroke of the press produce the desired form on the sheet...

 out of sheet metal. A few suppressors for low-powered cartridges such as the .22 Long Rifle
.22 Long Rifle
The .22 Long Rifle rimfire cartridge is a long established variety of ammunition, and in terms of units sold is still by far the most common in the world today. The cartridge is often referred to simply as .22 LR and various rifles, pistols, revolvers, and even some smoothbore shotguns have...

 have successfully used plastic baffles (certain models by Vaime and others.)

Baffles are separated by spacers, which keep them aligned at a specified distance apart inside the suppressor. Many baffles are manufactured as a single assembly with its spacer, and several suppressor designs have all the baffles attached together with spacers as a one-piece helical baffle stack. Modern baffles are usually carefully shaped to divert the propellant gases effectively into the chambers. This shaping can be a slanted flat surface, canted at an angle to the bore, or a conical or otherwise curved surface. One popular technique is to have alternating angled surfaces through the stack of baffles.

Baffles come in several designs. M, K, Z, Monolithic Core and Ω(Omega) are the most prevalent. M-type is the crudest and composes an inverted cone
Cone (geometry)
A cone is an n-dimensional geometric shape that tapers smoothly from a base to a point called the apex or vertex. Formally, it is the solid figure formed by the locus of all straight line segments that join the apex to the base...

. K forms slanted obstructions diverging from the sidewalls, creating turbulence
Turbulence
In fluid dynamics, turbulence or turbulent flow is a flow regime characterized by chaotic and stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time...

 across the bore
Gauge (bore diameter)
The gauge of a firearm is a unit of measurement used to express the diameter of the barrel. Gauge is determined from the weight of a solid sphere of lead that will fit the bore of the firearm, and is expressed as the multiplicative inverse of the sphere's weight as a fraction of a pound . Thus...

line. Z is expensive to machine and includes "pockets" of dead airspace along the sidewalls which trap expanded gases and hold them thereby lengthening the time that the gases cool before exiting. Omega is an advanced design combining elements of all three previous designs. Omega forms a series of spaced cones drawing gas away from the boreline, incorporates a scallopped mouth creating cross-bore turbulence, which is in turn directed to a "mouse-hole" opening between the baffle stack and sidewall. They were created and developed by Joe Gadinni, and are in use by SWR Manufacturing.

Baffles usually last for a significant number of firings. Propellant gas heats and erodes the baffles, causing wear, which is worsened by high rates of fire. Aluminium baffles are seldom used with fully automatic weapon
Automatic firearm
An automatic firearm is a firearm that loads another round mechanically after the first round has been fired.The term can be used to refer to semi-automatic firearms, which fire one shot per single pull of the trigger , or fully automatic firearms, which will continue to load and fire ammunition...

s, because service life is unacceptably short. Some modern suppressors using steel or high-temperature alloy baffles can endure extended periods of fully automatic fire without damage. The highest-quality rifle suppressors available today have a claimed service life of greater than 30,000 rounds. Baffles have not been given any specific angles, a specific size, or weight to meet any standards; they are created on a trial and error basis.

Wipes are inner dividers intended to touch the bullet as it passes through the suppressor, and are typically made of rubber
Rubber
Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...

, plastic
Plastic
A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...

 or foam
Foam
-Definition:A foam is a substance that is formed by trapping gas in a liquid or solid in a divided form, i.e. by forming gas regions inside liquid regions, leading to different kinds of dispersed media...

. Each wipe may either have a hole drilled in it before use, a pattern stamped into its surface at the point where the bullet will strike it, or it may simply be punched through by the bullet. Wipes typically last for a small number of firings (perhaps no more than five) before their performance is significantly degraded. While many suppressors used wipes in the Vietnam War
Vietnam War
The Vietnam War was a Cold War-era military conflict that occurred in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. This war followed the First Indochina War and was fought between North Vietnam, supported by its communist allies, and the government of...

 era, most modern suppressors do not use them to minimize disassembly and parts replacement.

"Wet" suppressors or "wet cans" use a small quantity of water, oil
Oil
An oil is any substance that is liquid at ambient temperatures and does not mix with water but may mix with other oils and organic solvents. This general definition includes vegetable oils, volatile essential oils, petrochemical oils, and synthetic oils....

, grease
Petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...

 or gel
Gel
A gel is a solid, jelly-like material that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state...

 in the expansion chambers to cool the propellant gases and reduce their volume (see ideal gas law
Ideal gas law
The ideal gas law is the equation of state of a hypothetical ideal gas. It is a good approximation to the behavior of many gases under many conditions, although it has several limitations. It was first stated by Émile Clapeyron in 1834 as a combination of Boyle's law and Charles's law...

). The coolant lasts only a few shots before it must be replenished, but can greatly increase the effectiveness of the suppressor. Water is most effective, due to its high heat of vaporization, but it can run or evaporate out of the suppressor. Grease, while messier and less effective than water, can be left in the suppressor indefinitely without losing effectiveness. Oil is the least effective and least preferable, as it runs while being as messy as grease, and leaves behind a fine mist of aerosol
Aerosol
Technically, an aerosol is a suspension of fine solid particles or liquid droplets in a gas. Examples are clouds, and air pollution such as smog and smoke. In general conversation, aerosol usually refers to an aerosol spray can or the output of such a can...

ized oil after each shot. Water-based gels, such as wire-pulling lubricant gel, are a good compromise; they offer the efficacy of water with less mess, as they do not run or drip. However, they take longer to apply, as they must be cleared from the bore of the suppressor to ensure a clear path for the bullet (grease requires this step as well). Generally, only pistol suppressors are shot wet, as rifle suppressors handle such high pressure and heat that the liquid is gone within 1-3 shots. Many manufacturers will not warranty their rifle suppressors for "wet" fire, as some feel this may even result in a dangerous over-pressurization of the silencer.

Packing materials such as metal mesh
Mesh
Mesh consists of semi-permeable barrier made of connected strands of metal, fiber, or other flexible/ductile material. Mesh is similar to web or net in that it has many attached or woven strands.-Types of mesh:...

, steel wool
Steel wool
Steel wool, also known as wire wool, is a bundle of strands of very fine soft steel filaments, used in finishing and repairing work to polish wood or metal objects, and for cleaning household cookware....

 or metal washers
Washer (hardware)
A washer is a thin plate with a hole that is normally used to distribute the load of a threaded fastener, such as a screw or nut. Other uses are as a spacer, spring , wear pad, preload indicating device, locking device, and to reduce vibration...

 may be used to fill the chambers and further dissipate and cool the gases. These are somewhat more effective than empty chambers, but less effective than wet designs. Metal mesh, if properly used, may last for hundreds or thousands of shots of spaced semi-automatic fire, however steel wool usually degrades within ten shots with stainless wool lasting longer than regular steel wool. Like wipes, packing materials are rarely found in modern suppressors.

Wipes, packing materials and purpose-designed wet cans have been generally abandoned in 21st-century suppressor design because they decrease overall accuracy and require excessive cleaning and maintenance. The instructions from several manufacturers state that their suppressors need not be cleaned at all. Furthermore, legal changes in the United States during the 1980s and 1990s made it much more difficult for end-users to legally replace internal silencer parts, and the newer designs reflect this reality.

Advanced types

In addition to containing and slowly releasing the gas pressure associated with muzzle blast or reducing pressure through the use of coolant mediums, advanced suppressor designs attempt to modify the properties of the sound waves generated by the muzzle blast. In these designs, effects known as frequency shifting and phase cancellation (or destructive interference) are used in an attempt to make the suppressor quieter. These effects are achieved by separating the flow of gases and causing them to collide with each other or by venting them through precision-made holes. The intended effect of frequency shifting is to shift audible sound waves frequencies into ultrasound
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...

 (above 20 kHz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....

), beyond the range of human hearing. The Russian AN-94
AN-94
The AN-94 is an advanced Russian assault rifle. The initials stand for Avtomat Nikonova Model of 1994....

 assault rifle features a muzzle attachment that claims apparent noise reduction by venting some gases through a "dog-whistle" type channel. Phase cancellation occurs when similar sound wave frequencies encounter each other 180° out of phase, cancelling the amplitude of the wave and eliminating the pressure variations perceived as sound.

Using either property to advantage requires that the suppressor be designed within the specification of the muzzle blast in mind. For example, the velocity of the sound waves is a major factor. This figure can change significantly between different cartridges and barrel lengths.

Thus, in order for maximum effectiveness to be achieved, the suppressor must be "tuned" for a specific cartridge/barrel length combination. This can be done through the use of either a fixed or adjustable baffle design. While it may sound daunting, any weapon that needs to provide such exceptional sound suppression is almost certainly going to be manufactured in small quantities and issued only for mission profiles critical enough to make such efforts worthwhile.

However, these concepts are controversial because muzzle blast creates broadband noise
White noise
White noise is a random signal with a flat power spectral density. In other words, the signal contains equal power within a fixed bandwidth at any center frequency...

 rather than pure tone
Pure tone
A pure tone is a tone with a sinusoidal waveshape.A sine wave is characterized by its frequency, the number of cycles per second—or its wavelength, the distance the waveform travels through its medium within a period—and the amplitude, the size of each cycle...

s, and phase cancellation in particular is therefore extremely difficult (if not impossible) to achieve. Some suppressor manufacturers claim to use phase cancellation in their designs, but these claims are generally unsupported from a scientific perspective.

From the practical perspective, supersonic
Supersonic
Supersonic speed is a rate of travel of an object that exceeds the speed of sound . For objects traveling in dry air of a temperature of 20 °C this speed is approximately 343 m/s, 1,125 ft/s, 768 mph or 1,235 km/h. Speeds greater than five times the speed of sound are often...

 cartridge loads are impractical to suppress past the levels that are merely hearing-safe for the shooter due to the sonic boom emitted by the bullet, and cartridges such as .22 LR and .45 ACP
.45 ACP
The .45 ACP , also known as the .45 Auto by C.I.P., is a cartridge designed by John Browning in 1904, for use in his prototype Colt semi-automatic .45 pistol and eventually the M1911 pistol adopted by the United States Army in 1911.-Design and history:The U.S...

 have long been recognized as easy to suppress even if using technology dating back to 1940s when the mission calls for the quietest gun available.

Sources of firearm noise

The portrayal of suppressed firearms in popular culture is not always accurate and could lead to the misconception that silencers are capable of completely eliminating the sound of firing, or reducing it to a quiet whistling or "phut" sound. This is unlikely because when a gun is fired, multiple sounds are possibly made. There are five major categories of suppressed fire noise: action, blast, sonic signature, impact, and operator. Some of these are present in all instances, others depend wholly on the specific mechanics of the weapon employed.

In order of timing:
  • Action noise required to ignite the round.
  • Muzzle blast resulting from the discharge of propellant gas from the end of the barrel.
  • Sonic signature of the projectile in flight (supersonic velocity rounds).
  • Action noise in some firearm variants as the spent round is discharged and a fresh round reloaded.
  • Impact noise created as the projectile finds terminal impact.


The two loudest sounds in a gunshot are typically the muzzle blast and the sonic signature. Paired reports from the same shot may be observed when the listener is first reached by the shock wave generated by the bullet flying past at supersonic speed, then by the muzzle blast moving at sound speed all the way from the muzzle.

Multiple techniques are used to address each of these sounds, but the suppressor itself is capable of addressing muzzle blast, sonic signature (through integral gas bleed, at the price of reducing projectile speed to subsonic) and the ability to cancel the mechanical action noise through Nielsen device
Muzzle booster
A muzzle booster or recoil booster is a device affixed to the muzzle of a firearm, intended to harness the energy of the escaping propellant to augment the force of recoil on portions of the firearm. Muzzle boosters are usually used to improve the reliability of a recoil operated firearm...

 manipulation, canceling the ejection cycle.

Real world data

Live tests by independent reviewers of numerous commercially available suppressors find that even low caliber unsuppressed .22 LR firearms produce gunshots over 160 decibels. In testing, most of the suppressors reduced the volume to between 130 and 145 dB, with the quietest suppressors metering at 117 dB. The actual suppression of sound ranged from 14.3 to 43 dB, with most data points around the 30 dB mark. A notable example, the De Lisle carbine
De Lisle carbine
The De Lisle carbine or De Lisle Commando carbine was a British carbine used during World War II. The primary feature of the De Lisle was its very effective suppressor...

, a British WW II suppressed rifle used by Special Forces, was recorded at 85.5 dB in official firing tests.

Comparatively, ear protection commonly used while shooting provides 18 to 32 dB of sound reduction at the ear. Further, chainsaws, rock concerts, rocket engines, pneumatic drills, small firecrackers, and ambulance sirens are rated at 100 to 140 dB.

While some consider the noise reduction of a suppressor significant enough to permit safe shooting without hearing protection ("hearing safe"), noise-induced hearing loss may occur at 85 time-weighted-average decibels or above if exposed for a prolonged period, and suppressed gunshots regularly meter above 130 dB. However, the US Occupational Safety and Health Administration
Occupational Safety and Health Administration
The United States Occupational Safety and Health Administration is an agency of the United States Department of Labor. It was created by Congress of the United States under the Occupational Safety and Health Act, signed by President Richard M. Nixon, on December 29, 1970...

 uses 140 dB as the "safety cutoff" for impulsive noise
Impulse noise (audio)
Impulse noise is a category of noise which includes unwanted, almost instantaneous sharp sounds . Noises of the kind are usually caused by electromagnetic interference, scratches on the recording disks, and ill synchronization in digital recording and communication...

, which has led most US manufacturers to advertise sub-140 dB suppressors as "hearing safe."

Limitations of dB meter effectiveness

dB testing measures only the peak sound "pressure" noise, not duration or frequency. Limitations of dB testing become apparent in a comparison of sound between a .308 caliber
.308 Winchester
The .308 Winchester is a rifle cartridge and is the commercial cartridge upon which the military 7.62x51mm NATO centerfire cartridge is based. The .308 Winchester was introduced in 1952, two years prior to the NATO adoption of the 7.62x51mm NATO T65...

 rifle and a .300 Winchester Magnum
.300 Winchester Magnum
The .300 Winchester Magnum is a popular, belted, bottlenecked magnum rifle cartridge that was introduced by Winchester Repeating Arms Company in 1963 as a member of the family of Winchester Magnum cartridges. The .300 Winchester Magnum is a magnum cartridge designed to fit in a standard length...

 rifle. The dB meter will show that both rifles produce the same decibel level of noise. Upon firing these rifles, however, it is clear that the .300 Winchester Magnum sounds much louder. What the decibel meter does not show is that although both rifles produce the same peak sound pressure level (SPL), the .300 Winchester Magnum holds its peak duration longer. The .300 Winchester Magnum sound remains at full value longer, while the .308 goes to peak and falls off more quickly. dB meters fail in this and other regards when being used as the principal means to determine suppressor capability.

Caliber versus volume

The caliber and power of the bullet/cartridge being suppressed is also an important factor. Generally, equal quality suppressors can quiet the report of a smaller caliber bullet more effectively than a larger caliber bullet. This is because the exhaust gases can move more quickly through the exit hole necessary for larger caliber bullets. Likewise, cartridges which produce higher pressures and more gases, such as those used in rifles, will also generally be louder than those which produce less pressure and fewer gases, such as handgun cartridges. In a gunshot, the sound of the report (the combination of the sonic boom
Sonic boom
A sonic boom is the sound associated with the shock waves created by an object traveling through the air faster than the speed of sound. Sonic booms generate enormous amounts of sound energy, sounding much like an explosion...

, the vacuum release, and burn of powder) will almost always be louder than the sound of the action cycling of an auto-loading firearm
Semi-automatic firearm
A semi-automatic, or self-loading firearm is a weapon which performs all steps necessary to prepare the weapon to fire again after firing—assuming cartridges remain in the weapon's feed device or magazine...

. Alan C. Paulson, a renowned firearms specialist, claimed to have encountered an integrally suppressed .22 LR that had such a quiet report, although this is somewhat uncommon.

Because of the limited stopping power of less powerful cartridges, movie scenes in which an attacker fires a near-silent shot that instantly kills the victim are generally unrealistic; excepting headshots that admit the projectile directly into the cranial cavity and/or chest shots that hit the left ventricle or aorta.

Subsonic ammunition versus volume

In weapons firing supersonic bullets, the supersonic
Supersonic
Supersonic speed is a rate of travel of an object that exceeds the speed of sound . For objects traveling in dry air of a temperature of 20 °C this speed is approximately 343 m/s, 1,125 ft/s, 768 mph or 1,235 km/h. Speeds greater than five times the speed of sound are often...

 bullet itself produces a loud and very sharp sound as it leaves the muzzle in excess of the speed of sound and gradually reducing speed as it travels downrange. This is a small sonic boom
Sonic boom
A sonic boom is the sound associated with the shock waves created by an object traveling through the air faster than the speed of sound. Sonic booms generate enormous amounts of sound energy, sounding much like an explosion...

, and is referred to in the firearm field as "ballistic crack". Subsonic ammunition reduces this sound, but at the cost of lower velocity, often resulting in decreased range and effectiveness on the target. Military marksmen and police units may use this ammunition to maximize the effectiveness of their silenced rifles. While the range may be decreased when using subsonic rounds, this may be acceptable for specialized situations, where the absolute minimum amount of noise is required.

However, the numeric effectiveness of subsonic rounds is, again, misrepresented by media. Independent testing of commercially available firearm suppressors with commercially available subsonic rounds has found that .308 subsonic rounds decreased the volume at the muzzle 10 to 12 dB when compared to the same caliber of suppressed supersonic ammunition. When combined with suppressors, the subsonic .308 rounds metered between 121 and 137 dB.

This ballistic crack depends on the speed of sound, which in turn depends mainly on air temperature. At sea level, an ambient temperature of 70 °F (21 °C), and under normal atmospheric conditions, the speed of sound is approximately 1140 feet (347.5 m) per second (347 m/s). Bullets that travel near the speed of sound are considered transonic
Transonic
Transonic speed is an aeronautics term referring to the condition of flight in which a range of velocities of airflow exist surrounding and flowing past an air vehicle or an airfoil that are concurrently below, at, and above the speed of sound in the range of Mach 0.8 to 1.2, i.e. 600–900 mph...

, which means that the airflow over the surface of the bullet, which at points travels faster than the bullet itself, can break the speed of sound. Pointed bullets which gradually displace air can get closer to the speed of sound than round nosed bullets before becoming transonic.

Because merely reducing the propellant in a cartridge to get a slower bullet would lead to less stopping power, special cartridges have been developed specifically to maximize the energy available when used with a suppressor. These cartridges use very heavy bullets to make up for the energy lost by keeping the bullet subsonic. A good example of this is the .300 Whisper
.300 Whisper
The .300 Whisper is a wildcat cartridge in the Whisper family, a group of cartridges developed in the early 1990s by J.D. Jones of SSK Industries...

 cartridge, which is formed from a necked-up .221 Remington Fireball
.221 Remington Fireball
The .221 Remington Fireball was created by Remington Arms Company in 1963 for use in their single-shot bolt-action pistol called the XP-100. This was a special round designed for an experimental pistol, and has the highest velocity of any commercial pistol cartridge.-History:In the early 1960s...

 cartridge case. The subsonic .300 Whisper fires up to a 250 grain (16.2 g), .30 caliber bullet at about 980 feet (298.7 m) per second (298 m/s), generating about 533 ft·lbf (722 J) of energy at the muzzle. While this is similar to the energy available from the .45 ACP
.45 ACP
The .45 ACP , also known as the .45 Auto by C.I.P., is a cartridge designed by John Browning in 1904, for use in his prototype Colt semi-automatic .45 pistol and eventually the M1911 pistol adopted by the United States Army in 1911.-Design and history:The U.S...

 pistol cartridge, the reduced diameter and streamlined shape of the heavy .30 caliber bullet provides far better external ballistic
External ballistics
External ballistics is the part of the science of ballistics that deals with the behaviour of a non-powered projectile in flight. External ballistics is frequently associated with firearms, and deals with the behaviour of the bullet after it exits the barrel and before it hits the target.-Forces...

 performance, improving range substantially.

9×19mm Parabellum, a very popular caliber for suppressed shooting, can use almost any factory-loaded 147 gr (9.5 g) weight round to achieve subsonic performance. These 147 gr weight bullets typically have a velocity between 900 and 980 feet (298.7 m) per second (275 and 300 m/s), which is less than the common 1140 ft/s speed of sound.

Russian 9×39mm ammo had a high subsonic ballistic coefficient
Ballistic coefficient
In ballistics, the ballistic coefficient of a body is a measure of its ability to overcome air resistance in flight. It is inversely proportional to the negative acceleration—a high number indicates a low negative acceleration. BC is a function of mass, diameter, and drag coefficient...

, high retained downrange energy, high sectional density
Sectional density
Sectional density is the ratio of an object's mass to its cross-sectional area. It conveys how well an object's mass is distributed to overcome resistance. For illustration, a needle can penetrate a target medium with less force than a coin of the same mass...

, and moderate recoil
Recoil
Recoil 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, according to Newton's third law...

. All elements combined make this a very attractive choice for close quarters combat (CQB) firearms.

Instead of using subsonic ammunition, one can also lower the muzzle velocity
Muzzle velocity
Muzzle velocity is the speed a projectile has at the moment it leaves the muzzle of the gun. Muzzle velocities range from approximately to in black powder muskets , to more than in modern rifles with high-performance cartridges such as the .220 Swift and .204 Ruger, all the way to for tank guns...

 of a supersonic bullet before it leaves the barrel. Some suppressor designs, referred to as "integrals", do this by allowing gas to bleed off along the length of the barrel before the projectile exits. The MP5SD is the best example of this with holes right after the chamber of the barrel used to reduce a regular 115 or 124 gr ammo to subsonic velocities.

Identification

Aside from reductions in volume, suppressors also tend to alter the sound to something that is not identifiable as a gunshot. This reduces or eliminates attention drawn to the shooter (hence the Finnish
Finland
Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

 expression: "A silencer does not make a marksman silent, but it does make him invisible
Invisibility
Invisibility is the state of an object that cannot be seen. An object in this state is said to be invisible . The term is usually used as a fantasy/science fiction term, where objects are literally made unseeable by magical or technological means; however, its effects can also be seen in the real...

"). This is especially true in cases where there are other sources of ambient noise, such as in an urban environment. Suppressors are particularly useful in enclosed spaces where the sound, flash and pressure effects of a weapon being fired are amplified. Such effects may disorient the shooter, affecting situational awareness, concentration and accuracy, and can permanently damage hearing very quickly.

As the suppressed sound of firing is overshadowed by ballistic crack, observers can be deceived as to the location of the shooter, often from 90 to 180 degrees from his actual location. However, counter-sniper tactics
Counter-sniper tactics
Counter-sniper tactics involves tactics used by a sniper against another sniper.The occurrence of sniper warfare has led to the evolution of many counter-sniper tactics in modern military strategies...

 can include Gunshot Location Detection Systems, where sensitive microphones are coupled to computer algorithms, and use the ballistic crack to detect and localize the origin of the shot. The U.S. Boomerang
Boomerang (mobile shooter detection system)
Boomerang is a gunfire locator developed by DARPA and BBN Technologies primarily for use against snipers on mobile vehicles such as the Humvee, Stryker, and MRAP combat vehicles. There were future plans to integrate it into the Land Warrior system....

 system is one such example.

Other advantages

There are many advantages in using a suppressor that are not related to the sound.

Hunters using centerfire rifles find suppressors bring various important benefits that outweigh the extra weight and resulting change in the firearm's center of gravity. The most important advantage of a suppressor is the hearing protection for the shooter as well as his/her companions. There are many hunters who have suffered permanent hearing damage due to someone else firing a high-caliber gun too closely without a warning. By reducing noise, recoil and muzzle-blast, it also enables the firer to follow through calmly on his first shot and fire a further carefully aimed shot without delay if necessary. Wildlife
Wildlife
Wildlife includes all non-domesticated plants, animals and other organisms. Domesticating wild plant and animal species for human benefit has occurred many times all over the planet, and has a major impact on the environment, both positive and negative....

 of all kinds are often confused as to the direction of the source of a well-suppressed shot. In the field, however, the comparatively large size of a centerfire rifle suppressor can cause unwanted noise if it bumps or rubs against vegetation or rocks, and many users cover them with neoprene
Neoprene
Neoprene or polychloroprene is a family of synthetic rubbers that are produced by polymerization of chloroprene. Neoprene in general has good chemical stability, and maintains flexibility over a wide temperature range...

 sleeves.

Suppressors reduce firing recoil
Recoil
Recoil 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, according to Newton's third law...

 significantly, primarily by diverting and trapping the propellant gas. Propellant mass is generally a fraction of the projectile mass, but it exits the muzzle at multiples of the projectile velocity, and since recoil energy is a function of mass times velocity squared the elimination of the propellant recoil can be significant. Paulson et al., discussing low-velocity pistol calibers, suggest the recoil reduction is around 15%. With high-velocity calibers recoil reduction runs in the range of 20–30%. The added weight of the suppressor—normally 300 to 500 grams—also contributes to the reduction of the recoil. Further, the pressure against the face of each baffle is higher than the pressure on its reverse side, making each baffle a miniature "pneumatic ram" which pulls the suppressor forward on the weapon, contributing a counter recoil force.

A suppressor also cools the hot gases coming out of the barrel enough that most of the lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

-laced vapor
Vapor
A vapor or vapour is a substance in the gas phase at a temperature lower than its critical point....

 that leaves the barrel condenses
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....

 inside the suppressor, reducing the amount of lead that might be inhaled by the shooter and others around them. However, in auto-loading actions this might be offset by increased back pressure which results in propellant gas blowing back into a shooter's face through the chamber during case ejection.

Regulation

Legal regulation of suppressors varies widely around the world. In some nations, such as Finland
Finland
Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

, Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

 and France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

, some or all types of suppressor are essentially unregulated and may be bought "over the counter" in retail stores or by mail-order, as they are considered a great help, along with hearing protection, to preserve the hearing of the user and any onlookers.

Asia

In Hong Kong
Hong Kong
Hong Kong is one of two Special Administrative Regions of the People's Republic of China , the other being Macau. A city-state situated on China's south coast and enclosed by the Pearl River Delta and South China Sea, it is renowned for its expansive skyline and deep natural harbour...

, "any accessory to such arms designed or adapted to diminish the noise or flash" is within the definition of 'arms' under the Firearms and Ammunition Ordinance (HK Laws. Chap 238). As such, a permit is required (as with firearms and ammunition) for possession which would otherwise be illegal and carries penalties up to a fine of HK$100,000 and 14 years in jail.

In Thailand
Thailand
Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...

, sound suppressors of any kind are allowed to be used only by law enforcement units or military personnel in operation.

In Turkey
Turkey
Turkey , known officially as the Republic of Turkey , is a Eurasian country located in Western Asia and in East Thrace in Southeastern Europe...

, civilian purchase, sale or possession of suppressors are strictly prohibited, with possible jail terms of up to 25 years if convicted. Suppressors can only be purchased by military personnel when approved by the officer in charge of the base armory
Armory (military)
An armory or armoury is a place where arms and ammunition are made, maintained and repaired, stored, issued to authorized users, or any combination of those...

. Individual law enforcement officers are not eligible to purchase or possess suppressors unless these are issued by a local agency, in which case these would be registered to the General Directorate of Security
Law enforcement in Turkey
Law enforcement in Turkey is carried out by several departments and agencies, all acting under the command of the Prime Minister of Turkey or mostly the Minister of Internal Affairs....

 in Ankara
Ankara
Ankara is the capital of Turkey and the country's second largest city after Istanbul. The city has a mean elevation of , and as of 2010 the metropolitan area in the entire Ankara Province had a population of 4.4 million....

.

Europe

In Austria
Austria
Austria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...

, the purchase or possession of a suppressor is prohibited according to §17 of the Austrian Weapons Law.

In the Czech Republic
Czech Republic
The Czech Republic is a landlocked country in Central Europe. The country is bordered by Poland to the northeast, Slovakia to the east, Austria to the south, and Germany to the west and northwest....

 suppressors are, according to §4 of Weapons and Ammunition Law, considered an A-class weapon, which means a special exception is needed to possess them. This makes suppressors illegal for any practical purpose.

In Denmark
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...

, the Danish Weapons And Explosives Law makes the unlicensed possession of a suppressor illegal. A permit may be acquired from the local police, but permission is almost always denied. Only police and hunters with special permission for the emergency slaughtering of livestock inside buildings are allowed to use them.

In Finland
Finland
Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

, suppressors are not classified as "weapon parts". Therefore, they are completely legal in all calibers, requiring no registration or permit. As a somewhat generalized rule of thumb, Finnish gun law classifies only parts subject to firing pressure directly involved with firing the cartridge as weapon parts; barrels, bolts, and any part with a chamber. These are restricted to owners with a valid permit. All other parts and accessories are not weapon parts under this classification. This would include parts like magazines, various sights and scopes, and also suppressors.

In Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 suppressors are to be handled in the same way as the guns they are intended to be equipped with. That is, if a firearm requires a specific permit, the corresponding suppressor requires the identical permit as well. For example, suppressors for freely available airguns are also freely available. Firearm suppressors require a "legal need" to own them, just like the firearms they are designed for, but it is nigh on impossible to legally prove that you need a suppressor, with the exception of large city and graveyard pest control.

In Hungary
Hungary
Hungary , officially the Republic of Hungary , is a landlocked country in Central Europe. It is situated in the Carpathian Basin and is bordered by Slovakia to the north, Ukraine and Romania to the east, Serbia and Croatia to the south, Slovenia to the southwest and Austria to the west. The...

, the purchase or possession of a suppressor is prohibited for civilians.

Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

 prohibits the purchase or possession of a suppressor except for military personnel.

In the Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...

 suppressors are only legal if used for airguns. All other civilian use and ownership is prohibited by law.

In Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

, suppressors can be bought by anyone.

In Poland
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...

, suppressors are not classified as "important weapon parts". Therefore, they are completely legal in all calibers, requiring no registration or permit. However using suppressors (even installing) with a firearm is prohibited. Only police and military are allowed to use them.

In the Russian Federation, usage of firearm suppressors (legally defined as "devices for noiseless shooting") by civilians is prohibited, and the dealers are prohibited from selling them, but there is no penalty for purchasing or possession of such devices. Also the law lacks any straight definition of what a "device for noiseless shooting" is, or what decibel level is considered to be "noiseless", therefore it is completely up to the expert investigating the device whether it would be considered a "device for noiseless shooting" or not. That concerns not only specifically designed sound suppressors, but also such devices as muzzle compensators and flash suppressors. Sound moderators are very often used for airguns.

In Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

, suppressors for specified calibers are legal for hunting purposes. A license is required, but is normally always granted.

In the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, sales of suppressors fall into four categories of use. For replica and air weapons
Air gun
An air gun is a rifle , pistol , or shotgun that fires projectiles by means of compressed air or other gas, in contrast to a firearm, which burns a propellant. Most air guns use metallic projectiles as ammunition. Air guns that only use plastic projectiles are classified as airsoft...

, the purchase of a suppressor requires no license and in most cases, no identification requirement. For shotguns, these will probably require the presentation of the buyer's shotgun certificate but will not be recorded. If the shotgun is classified as a firearm (where capacity exceeds 3 cartridges) the firearm certificate (FAC) will need to show permission for the purchase of a suppressor. For a small- or full-bore rifle, the firearm certificate (FAC) will need to show permission for the purchase of a suppressor and also the gun for which it is intended. All firearms certificates have the firearm and caliber approved by the police and annotated to the document before a suppressor may be purchased. Police forces usually approve applications for a suppressor for hunting and target shooters, as the risks of litigation for personal injury, especially high-tone deafness resulting from shooting-induced hearing loss, are significant; and noise pollution
Noise pollution
Noise pollution is excessive, displeasing human, animal or machine-created environmental noise that disrupts the activity or balance of human or animal life...

 in general is a problem for shooting sports.

North America

In Canada
Gun politics in Canada
Gun politics in Canada is largely polarized between two groups with opposing views. One group includes those who object to the registration of personal firearms...

, a device to muffle or stop the sound of a firearm is a "prohibited device" under the Criminal Code. A prohibited device is not inherently illegal in Canada but it does require an uncommon and very specific prohibited device license for its possession, use, and transport. Suppressors cannot be imported into the country by civilians; special licensing is required for businesses to import and sell suppressors, and they are typically only available to law enforcement, conservation agencies and the military.

In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, taxes and strict regulations affect the manufacture and sale of suppressors under the National Firearms Act
National Firearms Act
The National Firearms Act , 73rd Congress, Sess. 2, ch. 757, , enacted on June 26, 1934, currently codified as amended as , is an Act of Congress that, in general, imposes a statutory excise tax on the manufacture and transfer of certain firearms and mandates the registration of those firearms. The...

. They are legal for individuals to possess and use for lawful purposes in thirty nine of the fifty states. However, a prospective user must go through an application process administered by the Bureau of Alcohol, Tobacco, Firearms and Explosives
Bureau of Alcohol, Tobacco, Firearms and Explosives
The Bureau of Alcohol, Tobacco, Firearms and Explosives is a federal law enforcement organization within the United States Department of Justice...

 (ATF), which requires a Federal tax payment of USD 200.00 and a thorough criminal background check
Background check
A background check or background investigation is the process of looking up and compiling criminal records, commercial records and financial records of an individual....

. The USD 200.00 buys a tax stamp
Revenue stamp
A revenue stamp, tax stamp or fiscal stamp is a adhesive label used to collect taxes or fees on documents, tobacco, alcoholic drinks, drugs and medicines, playing cards, hunting licenses, firearm registration, and many other things...

, which is the legal document allowing possession of a suppressor. The market for used suppressors in the U.S. is consequently very poor, which has driven innovations in the field (buyers want the height of technology, because they are basically "stuck" with the purchase). Suppressors are available in other countries for under USD 40, but they can be of crude construction, using cheap materials and baffle designs. The following states have explicitly banned any civilian from possessing a suppressor: California, Delaware, District of Columbia, Hawaii, Illinois, Iowa, Massachusetts, Minnesota, New Jersey, New York, Rhode Island, and Vermont.

The Federal legal requirements to manufacture a suppressor in the United States are enumerated in Title 26
Internal Revenue Code
The Internal Revenue Code is the domestic portion of Federal statutory tax law in the United States, published in various volumes of the United States Statutes at Large, and separately as Title 26 of the United States Code...

, Chapter 53 of the United States Code
United States Code
The Code of Laws of the United States of America is a compilation and codification of the general and permanent federal laws of the United States...

. The individual states and several municipalities also have their specific requirements.

Oceania

Suppressors are banned in all Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

n states.

New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

 has no restrictions on the manufacture, sale, possession, or use of suppressors.

Naming

While suppressors are also referred to as "silencers", the latter is misleading because no firearm can be made completely silent, as the term "silencer" implies. Functionally, a suppressor is meant to diminish the report of a discharged round, or make its sound unrecognizable. Other sounds emanating from the weapon remain unchanged. Even subsonic bullets make distinct sounds by their passage through the air and striking targets, and supersonic bullets produce a small sonic boom
Sonic boom
A sonic boom is the sound associated with the shock waves created by an object traveling through the air faster than the speed of sound. Sonic booms generate enormous amounts of sound energy, sounding much like an explosion...

, resulting in a "ballistic crack". Semi-
Semi-automatic firearm
A semi-automatic, or self-loading firearm is a weapon which performs all steps necessary to prepare the weapon to fire again after firing—assuming cartridges remain in the weapon's feed device or magazine...

 and fully automatic
Automatic firearm
An automatic firearm is a firearm that loads another round mechanically after the first round has been fired.The term can be used to refer to semi-automatic firearms, which fire one shot per single pull of the trigger , or fully automatic firearms, which will continue to load and fire ammunition...

 firearms also make distinct noises as their actions cycle, ejecting the fired cartridge
Cartridge (firearms)
A cartridge, also called a round, packages the bullet, gunpowder and primer into a single metallic case precisely made to fit the firing chamber of a firearm. The primer is a small charge of impact-sensitive chemical that may be located at the center of the case head or at its rim . Electrically...

 case and loading a new round. Despite being misleading, the term "silencer" is still widespread.

Both the United States Department of Justice and the ATF (Bureau of Alcohol, Tobacco, Firearms and Explosive) refer to these devices as "silencers".

See also

  • MSP Groza silent pistol
    MSP Groza silent pistol
    The MSP Groza silent pistol is a double-barrel, derringer-type firearm designed in the Soviet Union in 1972. The firearm is chambered for the silent 7.62×38 SP-3 cartridge which is fed via a two-round clip. The weapon was designed at the behest of the Spetsnaz and KGB as an assassination weapon...

  • OTs-38 Stechkin silent revolver
    OTs-38 Stechkin silent revolver
    The OTs-38 Stechkin is a 5-shot, double-action revolver chambered in the silent 7.62x41.5mm SP-4 cartridge. The cartridge employs a captive piston so there is no flash or loud report upon discharge. As the cartridge is rimless, the cylinder is fed via full moon clips.The revolver features a...

  • Sound Blimp
    Sound blimp
    A Sound Blimp is a housing attached to a camera which reduces the sound caused by the shutter click, particularly SLRs. It is primarily used in film still photography, so as not to interfere with the shooting of principal photography, and also in other situations where sound is distracting:...

  • Title II weapons
    Title II weapons
    Title II weapons, or NFA firearms, are certain firearms, explosive munitions, and other devices which are heavily regulated in the United States by the National Firearms Act . Any violation of the NFA is a felony punishable by up to 10 years in prison...


External links

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