Slugthrower Sniper Rifle

In military and law enforcement terminology, a sniper rifle is a precision-rifle used to ensure more accurate placement of bullets at longer ranges than other small arms. It is a common misconception that any scoped rifle is a sniper rifle, and while certain long guns are more suited for the application than others, it is the act of using a weapon strategically as a sniper that designates it as such. A typical sniper rifle is built for optimal levels of accuracy, fitted with a telescopic sight and chambered for a military centerfire cartridge. The term is often used in the media to describe any type of accurized firearm fitted with a telescopic sight that is employed against human targets, although "sniping rifle" or "sniper's rifle" is the technically correct term for such a rifle.

The military role of a sniper (a term derived from the snipe, a bird which was difficult to hunt and shoot) dates back to the turn of the 18th century, but the true sniper rifle is a much more recent development. Advances in technology, specifically that of telescopic sights and more accurate manufacturing, allowed armies to equip specially trained soldiers with rifles that enable them to deliver precise shots over greater distances than regular infantry weapons. The rifle itself could be based on a standard rifle (at first, a bolt-action rifle); however, when fitted with a telescopic sight, it becomes a sniper rifle.

Classification
Modern sniper rifles can be divided into two basic classes: military and law enforcement.

Military
Sniper rifles manufactured for military service are often designed for very high durability, range, reliability, sturdiness, serviceability and repairability under adverse environmental and combat conditions, at the sacrifice of a small degree of accuracy. Military snipers and sharpshooters may also be required to carry their rifles and other equipment for long distances, making it important to minimize weight. Military organizations often operate under strict budget constraints, which influences the type and quality of sniper rifles they purchase.

Law enforcement
Sniper rifles built or modified for use in law enforcement are generally required to have the greatest possible accuracy, but do not need to have as long a range.

Law enforcement-specific rifles are usually used in non-combat (often urban) environments, so they do not have the requirement to be as hardy or portable as military versions; therefore, they may be smaller, because they do not need very long range.

Some of the first sniper rifles designed specifically to meet police and other law-enforcement requirements were developed for West German police after the Munich massacre at the 1972 Summer Olympics. Many police services and law enforcement organizations (such as the U.S. Secret Service) now use rifles designed for law enforcement purposes.

The Heckler & Koch PSG1 is one rifle specifically designed to meet these criteria and is often referred to as an ideal example of this type of sniper rifle. The FN Special Police Rifle was built for, and is marketed to, law enforcement rather than military agencies.

Distinguishing Characteristics
1 - Lead/deflection scale

2 - Main targeting chevron

3 - Bullet drop chevrons

4 - Rangefinder

The features of a sniper rifle can vary widely depending on the specific tasks it is intended to perform. Features that may distinguish a sniper rifle from other weapons are the presence of a telescopic sight, unusually long overall length, a stock designed for firing from a prone position, and the presence of a bipod and other accessories.

Telescopic Sight
The single most important characteristic that sets a sniper rifle apart from other military or police small arms is the mounting of a telescopic sight, which is relatively easy to distinguish from smaller optical aiming devices found on some modern assault rifles and submachine guns. This also allows the user to see farther.

The telescopic sights used on sniper rifles differ from other optical sights in that they offer much greater magnification (more than 4× and up to 40×), and have a much larger objective lens (40 to 50 mm in diameter) for a brighter image.

Most telescopic lenses employed in military or police roles have special reticles to aid with judgment of distance, which is an important factor in accurate shot placement due to the bullet's trajectory.

Action
The choice between bolt-action and semi-automatic (more commonly known as recoil or gas operation) is usually determined by specific requirements of the sniper's role as envisioned in a particular organization, with each design having advantages and disadvantages. For a given cartridge, a bolt-action rifle is cheaper to build and maintain, more reliable, and lighter, due to fewer moving parts in the mechanism. In addition, the absence of uncontrolled automatic cartridge case ejection helped to avoid revealing the firer's position. Semi-automatic weapons can serve both as battle rifle and sniper rifle, and allow for a greater rate (and hence volume) of fire. As such rifles may be modified service rifles, an additional benefit can be commonality of operation with the issued infantry rifle. A bolt action is most commonly used in both military and police roles due to its higher accuracy and ease of maintenance. Anti-materiel applications such as mine clearing and special forces operations tend to use semi-automatics.

A designated marksman rifle (DMR) is less specialized than a typical military sniper rifle, often only intended to extend the range of a group of soldiers. Therefore, when a semi-automatic action is used it is due to its ability to cross over into roles similar to the roles of standard issue weapons. There may also be additional logistical advantages if the DMR uses the same ammunition as the more common standard issue weapons. These rifles enable a higher volume of fire, but sacrifice some long range accuracy. They are frequently built from existing selective fire battle rifles or assault rifles, often simply by adding a telescopic sight and adjustable stock.

A police semi-automatic sniper rifle may be used in situations that require a single sniper to engage multiple targets in quick succession, and military semi-automatics such as the M110 SASS are used in similar "target-rich" environments.

Cartridge
In a military setting, logistical concerns are the primary determinant of the cartridge used, so sniper rifles are usually limited to rifle cartridges commonly used by the military force employing the rifle and match grade ammunition. Since large national militaries generally change slowly, military rifle ammunition is frequently battle-tested and well-studied by ammunition and firearms experts. Consequently, police forces tend to follow military practices in choosing a sniper rifle cartridge instead of trying to break new ground with less-perfected (but possibly better) ammunition.

Before the introduction of the standard 7.62×51mm NATO (.308 Winchester) cartridge in the 1950s, standard military cartridges were the .30-06 Springfield or 7.62×63mm (United States), .303 British (7.7×56mmR) (United Kingdom) and 7.92×57mm (8mm Mauser) (Germany). The .30-06 Springfield continued in service with U.S. Marine Corps snipers during the Vietnam War in the 1970s, well after general adoption of the 7.62×51mm. At the present time, in both the Western world and within NATO, 7.62×51mm is currently the primary cartridge of choice for military and police sniper rifles.

Worldwide, the trend is similar. The preferred sniper cartridge in Russia is another .30 caliber military cartridge, the 7.62×54 mm R, which has similar performance to the 7.62×51mm. This cartridge was introduced in 1891, and both Russian sniper rifles of the modern era, the Mosin-Nagant and the Dragunov sniper rifle, are chambered for it.

Certain commercial cartridges designed with only performance in mind, without the logistical constraints of most armies, have also gained popularity in the 1990s. These include the 7 mm Remington Magnum (7.2×64mm), .300 Winchester Magnum (7.8/7.62×67mm), and the .338 Lapua Magnum (8.6×70mm). These cartridges offer better ballistic performance and greater effective range than the 7.62×51mm. Though they are not as powerful as .50 caliber cartridges, rifles chambered for these cartridges are not as heavy as rifles chambered for .50 caliber ammunition, and are significantly more powerful than rifles chambered for 7.62×51mm.

Snipers may also employ anti-materiel rifles in sniping roles against targets such as vehicles, equipment and structures, or for the long-range destruction of explosive devices; these rifles may also be used against personnel.

Anti-materiel rifles tend to be semi-automatic and of a larger caliber than anti-personnel rifles, using cartridges such as the .50 BMG, 12.7×108mm Russian or even 14.5×114mm Russian and 20mm. These large cartridges are required to be able to fire projectiles containing payloads such as explosives, armor piercing cores, incendiaries or combinations of these, such as the Raufoss Mk211 projectile. Due to the considerable size and weight of anti-materiel rifles, 2- or 3-man sniper teams become necessary.

Barrel
Barrels are normally of precise manufacture and of a heavier cross section than more traditional barrels in order to reduce the change in impact points between a first shot from a cold barrel and a follow-up shot from a warm barrel. Unlike many battle and assault rifles, the bores are usually not chromed to avoid inaccuracy due to an uneven treatment.

When installed, barrels are often free-floated: i.e., installed so that the barrel only contacts the rest of the rifle at the receiver, to minimise the effects on impact point of pressure on the fore-end by slings, bipods, or the sniper's hands. The end of the barrel is usually crowned or machined to form a rebated area around the muzzle proper to avoid asymmetry or damage, and consequent inaccuracy. Alternatively, some rifles such as the Dragunov or Walther WA2000 provide structures at the fore-end to provide tension on the barrel in order to counteract barrel drop and other alterations in barrel shape.

External longitudinal fluting that contributes to heat dissipation by increasing surface area, while simultaneously decreasing the weight of the barrel, is sometimes used on sniper-rifle barrels.

Sniper-rifle barrels may also utilise a threaded muzzle or combination device (muzzle brake or flash suppressor and attachment mount) to allow the fitting of a sound suppressor. These suppressors often have a means of adjusting the point of impact while fitted.

Military sniper rifles tend to have barrel lengths of 609.6 mm (24 inches) or longer, to allow the cartridge propellant to fully burn, reducing the amount of revealing muzzle flash and increasing muzzle velocity. Police sniper rifles may use shorter barrels to improve handling characteristics. The shorter barrels' muzzle velocity loss is unimportant at closer ranges; the impact velocity of the bullet is more than sufficient.

Stock
The most common special feature of a sniper rifle stock is the adjustable cheek piece, where the shooter's cheek meets the rear of the stock. For most rifles equipped with a telescopic sight, this area is raised slightly, because the telescope is positioned higher than iron sights. A cheek piece is simply a section of the stock that can be adjusted up or down to suit the individual shooter. To further aid this individual fitting, the stock can sometimes also be adjusted for length, often by varying the number of inserts at the rear of the stock where it meets the shooter's shoulder. Sniper stocks are typically designed to avoid making contact with the barrel of the weapon.

Accessories
An adjustable sling is often fitted on the rifle, used by the sniper to achieve better stability when standing, kneeling, or sitting. The sniper uses the sling to "lock-in" by wrapping his non-firing arm into the sling forcing his arm to be still. Non-static weapon mounts such as bipods, monopods and shooting sticks are also regularly used to aid and improve stability and reduce operator fatigue.

Accuracy
A military-issue battle rifle or assault rifle is usually capable of between 3-6 minute of angle (MOA) (1-2 mrad) accuracy. A standard-issue military sniper rifle is typically capable of 1-3 MOA (0.3-1 mrad) accuracy, with a police sniper rifle capable of 0.25-1.5 MOA (0.1-0.5 mrad) accuracy. For comparison, a competition target or benchrest rifle may be capable of accuracy up to 0.15-0.3 MOA (0.05-0.1 mrad).

A 1 MOA (0.3 mrad) average extreme spread for a 5-shot group (meaning the center-to-center distance between the two most distant bullet holes in a shot-group) translates into a 69% probability that the bullet's point of impact will be in a target circle with a diameter of 23.3cm at 800m. This average extreme spread for a 5-shot group and the accompanying hit probability are considered sufficient for effectively hitting a human shape at 800 m distance.

In 1982 a U.S. Army draft requirement for a Sniper Weapon System was: "The System will: (6) Have an accuracy of no more than 0.75 MOA (0.2 mrad) for a 5-shot group at 1,500 meters when fired from a supported, non-benchrest position". Actual Sniper Weapon System (M24) adopted in 1988 has stated maximum effective range of 800 meters and a maximum allowed average mean radius (AMR) of 1.9 inches at 300 yards from a machine rest, what corresponds to a 0.6 MOA (0.5 mrad) extreme spread for a 5-shot group when using 7.62 × 51mm M118 Special Ball cartridges.

A 2008 United States military market survey for a Precision Sniper Rifle (PSR) calls for 1 MOA (0.3 mrad) extreme vertical spread for all shots in a 5-round group fired at targets at 300, 600, 900, 1,200 and 1,500 meters. In 2009 a United States Special Operations Command market survey calls for 1 MOA (0.3 mrad) extreme vertical spread for all shots in a 10-round group fired at targets at 300, 600, 900, 1,200 and 1,500 meters.

The 2009 Precession Sniper Rifle requirements state that the PSR when fired without suppressor shall provide a confidence factor of 80% that the weapon and ammunition combination is capable of holding 1 MOA extreme vertical spread. This shall be calculated from 150 ten (10) round groups that were fired unsuppressed. No individual group shall exceed 1.5 MOA (0.5 mrad) extreme vertical spread. All accuracy will be taken at the 1,500 meter point.

In 2008 the US military adopted the M110 Semi-Automatic Sniper System which has corresponding maximum allowed extreme spread of 1.8 MOA (0.5 mrad) for a 5-shot group on 300 feet, using M118LR ammunition or equivalent. In 2010 the maximum bullet dispersion requirement for the M24 .300 Winchester Magnum corresponds to 1.4 MOA extreme spread for 5 shot group on 100 meters.

Although accuracy standards for police rifles do not widely exist, rifles are frequently seen with accuracy levels from 0.5-1.5 MOA (0.2-0.5 mrad). For typical policing situations, an extreme spread accuracy level no better than 1 MOA (0.3 mrad) is usually all that is required. This is because police typically employ their rifles at short ranges. At 100 m or less, a rifle with a relatively low accuracy of only 1 MOA (0.3 mrad) should be able to repeatedly hit a 3 cm (1.2 inch) target. A 3 cm diameter target is smaller than the brain stem which is targeted by police snipers for its quick killing effect.