How to Use a Rifle Scope

Scopes assist riflemen by allowing them to see more precisely at further distances. The power can range from 1.5x to 50x for conventional rifles. When placed on a rifle, it is often "bore sighted" from the gunsmith (or, if you mount it, it isn't sighted at all). When the gun first gets taken to the range, the rifle must be zeroed. Which means that at distance X the bullet will land exactly where the reticle is aimed (not counting for any wind or elevation changes). Standard combat rifles or varmint rifles are usually zeroed at 100 yards (we will assume, from now on, 100 yards is zero distance).

1.Determine how far off target a bullet lands, then adjust the scope accordingly . This is the most conventional way to zero the scope.

Most scopes have windage and elevation knobs which can be turned to compensate for inaccuracies. The elevation is usually on the top and affects the bullet's point of impact (POI) vertically. The windage is usually on the right side of the scope and affects the bullet's POI horizontally.

2.Most scopes have either mil-dot or ballistiplex reticle which allows the shooter to easily line up a shot at distances further than the zeroed point.

Most scopes come with a chart to show based on the bullet's caliber, velocity, and weight where to line up the reticle. While the weight and caliber are easy to mimic, the velocity is a very specific thing to a rifle. You will likely have to create your own chart for your rifle if you wish to be as accurate as possible.

3.Know that while military snipers practice adjusting the wind-age and elevation for the specific situation, it usually isn't practical for hunters or recreational shooters to precisely measure wind speed and other factors to the target and adjust the scope It is often best to do approximate calculations and hold-off the reticle, so re-zeroing the scope is not necessary. There are many factors that need to be taken into account when adjusting the scope, here are a few of them (in general order of priority)

• Distance to target needs to be calculated for zeroing of the scope. When not at your zeroed distance, bullet drop or rise needs to be taken into account (read about zeroing above).
• Bullet velocity affects the amount of bullet drop.
• Cross wind affects how far to the left and right the bullet will land. Under 100 yards, this usually isn't too big of a factor, but with a lighter bullet at 300 yards and a 5MPH wind, the bullet landing point can move up to a foot.
• Bullet weight is also a big factor, especially at longer distances. It will determine the maximum effective range of a bullet (since heavier bullets have better aerodynamic coefficients), thus bullet trajectory, and how much cross wind will move the bullet.
• Aiming at a target at a different elevation (even if only a few yards) than yourself is known asshot angle. It is another variable that needs to be taken into account.
• All the lesser affects are often not considered, but they can still influence bullet flight path.Head/tail wind affects the long distance bullet velocity and trajectory. The distance from the ground and ground temperature compared to ambient (air) temperature can cause bullet lift. Often after a hot day, when the ground is warmer than the air, there will be less bullet drop, and vice versa. Humidity and temperature also have minute affects on bullet trajectory. On extremely long shots (more than 1000 yards) even the curvature of the earth should be accounted for if a pinpoint-accurate shot needs to be taken.
• There are computer or PDA calculators which can calculate the exact landing position of the bullet based on all the information above (at least the major points). The calculators usually assume you re-zero your reticle. That is the best way to be perfectly accurate, but for target shooting where you don't need a one-shot-one-kill, re-zeroing can be a lot of hassle.
• If you do adjust the reticle positions, you should try to keep track of how many clicks in each direction were used, so at the end of the day, you can set the scope back at its zero.

4.Adjust the parallax (if available) according to the distance your target is at. Many scopes (especially adjustable-power scopes) allow the shooter to place the reticle on the same distance plane as the target. This is essential to take an extremely accurate shot.

• Most parallaxes have distances listed on them. Though these numbers are often good guidelines they are rarely accurate. Based on the distance of the target, the shooter's eye relief, and power of the scope, the parallax will change minutely. Parallaxes are often very difficult to adjust accurately, but with a little practice you will be able to estimate the parallax position based on the distance to target.
• A way to "cheat" the parallax is to place your head in a relief position where you can see black around the edge while viewing down the scope. Move your head and eye to make the black area even on all edges around the reticle.
• While the parallax is important for an extremely precise shot, a parallax set at 150-yards (the standard distance for fixed parallax scopes) at 1000 yards, the reticle will be at a maximum of eight inches off (at closer distances it will be much less — at 500 yards a maximum of an inch and a half off).

5.Align the scope properly by placing the cross hairs in the center of your target at your zero distance. You may need to compensate for distance, angle, or headwind by raising or lowering the cross hairs, keeping the center line on target.

TIPS

• Depending on the selected bullet and rifle
  
  

  A few standard cross hairs.
  (you must do research or testing to find the case with your setup) the zero range may cause the bullet to be below the reticle before zero, then above after zero, and eventually falls again to (at a different distance) be lined up with the reticle again (this may be 120 yards or 300, and it will likely change from rifle to rifle, even in the same caliber). Another, more common, scenario is that the bullet climbs sooner, and from (say) 40 to 100 yards is above the reticle, it then falls to meet your zero, and from then on (100 and more yards) is below the reticle.

source: http://www.wikihow.com/Use-a-Rifle-Scope

SNIPER RIFFLE

In military and law enforcement terminology, a sniper rifle is a rifle used to ensure more accurate placement of bullets at longer ranges than other small arms. A typical sniper rifle is built for optimal levels of accuracy, fitted with a telescopic sight and chambered for a military centerfirecartridge. 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 fashion to refer to such a rifle.

The military role of 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.

In the American Civil War Confederate troops equipped with barrel-length three power scopes mounted on the exceptionally accurate British Whitworth rifle had been known to kill Union officers at ranges of about 800 yards (731.5m), an unheard-of distance at that time.^[1][2][3][4]

The earliest sniper rifles were little more than conventional military or target rifles with long-range "peep sights" and Galilean 'open telescope' front and rear sights, designed for use on the target range. Only from the beginning of World War I did specially adapted sniper rifles come to the fore. Germany deployed military caliber hunting rifles with telescopic sights, and the British used Aldis, Winchester and Periscopic Prism Co. sights fitted by gunsmiths to regulation SMLE Mk III and Mk III* or Enfield Pattern 1914 rifles; the Canadian Ross rifle was also employed by snipers after it had been withdrawn from general issue.

Typical World War II-era sniper rifles were generally standard-issue battle rifles, selected for accuracy, with a 2.5x or 3x telescopic sight and cheek-rest fitted and the bolt turned down if necessary to allow operation with the scope fitted. Australia's No.1 Mk III* (HT) rifle was a later conversion of the SMLE fitted with the Lithgow heavy target barrel at the end of WW2. By the end of the war, forces on all sides had specially trained soldiers equipped with sniper rifles, and they have played an increasingly important role in military operations ever since.

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 4x and up to 40x), 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.

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. 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 7.62x51mm_NATO cartridge in the 1950s, standard military cartridges were the .30-06 Springfield or 7.62x63mm (United States), .303 British (7.7x56mmR) (United Kingdom) and 7.92x57mm (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 7.62x51mm. At the present time, in both the Western world and within NATO, 7.62x51mm 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 calibre military cartridge, the 7.62 x 54 mm R, which has similar performance to the 7.62x51mm. This cartridge was introduced in 1891, and both Russian sniper rifles of the modern era, theMosin-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 (7.2x64mm), .300 Winchester Magnum (7.8/7.62x67mm), and the .338 Lapua Magnum (8.6x70mm). These cartridges offer better ballistic performance and greater effective range than the 7.62x51mm. Though they are not as powerful as .50 calibre cartridges they are not as heavy as rifles chambered for .50 calibre ammunition, and are significantly more powerful than rifles chambered for 7.62x51mm.

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 calibre than anti-personnel rifles, using cartridges such as the .50 BMG, 12.7x108mm Russian or even 14.5x114mm Russian and20mm. These large cartridges are required to be able to fire projectiles containing payloads such as explosives, armour 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 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 means of adjusting the point of impact while fitted.

Military sniper rifles tend to have barrel lengths of 600 mm (24 inches) or longer, to allow the cartridge propellant to fully burn, reducing revealing muzzle flash and increasing bullet velocity. Police sniper rifles may use shorter barrels to improve handling characteristics. The shorter barrels' velocity loss is unimportant at closer ranges; projectile energy is more than sufficient.

Accuracy

Comparison of 0.5, 1, and 3 MOA extreme spread levels against a human torso at 800 m (left) and a human head at 100 m (right)

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 69% probability that the bullet's point of impact will be in the circle with center in point of aim and diameter of 25 cm at 800 m (about 8 inches at 800 yards), which is considered sufficient to ensure a high probability of hitting a human shape at that 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".^[6] 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 1.6 MOA (0.5 mrad) extreme spread for a 5-shot group when using 7.62 x 51 mm M118 Special Ball cartridges.^[7][8][9]

Precision Weapon Engagement Ranges & Dispersion according to the US Army.

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.^[10][11] 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.^[12][13] 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.^[14][15] In 2008 the US military adopted the M110 Semi-Automatic Sniper Systemwhich 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.^[7][8][16] In 2010 maximum bullet dispersion requirement for M24 .300 Winchester Magnumcorresponds^[7][8] 1.4 MOA extreme spread for 5 shot group on 100 meters ^[17].

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)^[18]. 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.^[19] 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.^[20]

[edit]Maximum effective range

Cartridge	Maximum effective range[21][22]
7.62x39mm	350 m
5.56x45mm	550 m
7.62x51mm (.308 Winchester)	800 m
7.62x54mm R	800 m
.30-06 Springfield	800 m
7 mm Remington Magnum	900–1,100 m
.300 Winchester Magnum	900–1,200 m
.338 Lapua Magnum	1,200-1,500 m
.50 BMG (12.7x99mm NATO) 12.7x108mm (Russian)	1,500–2,000 m
14.5x114mm	1,800–2,300 m
.408 Chey Tac	2,300 m

Unlike police sniper rifles, military sniper rifles tend to be employed at the greatest possible distances so that range advantages like the increased difficulty to spot and engage the sniper can be exploited. The most popular military sniper rifles (in terms of numbers in service) are chambered for 7.62 mm (0.30 inch) caliber ammunition, such as7.62x51mm and 7.62x54mm R. Since sniper rifles of this class must compete with several other types of military weapons with similar range, snipers invariably must employ skilled fieldcraft to conceal their position.

The recent trend in specialised military sniper rifles is towards larger calibres that offer relatively favorable hit probabilities at greater range, such as the anti-personnel .338 Lapua Magnum cartridge and anti-materiel cartridges like the .50 BMG and the 14.5x114mm. This allows snipers to take fewer risks, and spend less time finding concealment when facing enemies that are not equipped with similar weapons.

Maximum range claims made by military organizations and materiel manufacturers regarding sniper weapon systems are not based on consistent or strictly scientific criteria. The problem is only the bullet interacts after a relatively long flight path with the target (can also be a materiel target for a sniper bullet). This implies that variables such as the minimal required hit probability, local atmospheric conditions, properties and velocity of the employed bullet (parts), properties of the target and the desired terminal effect are major relevant factors that determine the maximum effective range of the employed system.

source: http://en.wikipedia.org/wiki/Sniper_rifle