Sniper rifle

A sniper rifle is a type of rifle used for engaging in the act of sniping, most purely a rifle used for shooting with great accuracy over long distances.

Features

The key feature of modern sniper rifles is reliable placement of a bullet often at comparatively long distances, with a design that supports this goal. Common features include precision manufacture, a highly reliable gun action, a precise scope or optical system, and almost always some support device for the shooter to fire from multiple positions. The need for high reliability and simplicity has resulted in many modern rifles continuing to be bolt action, though many are semi-automatic. The scope is dependent on the rifle and intended engagement distance. Some large caliber sniper rifles are sighted out to 1500 m with ultra high-magnification scopes, while rifles intended for urban combat and more limited range would use much less magnification. Many modern rifles incorporate bipods to steady the rifle for accurate shooting.

Related Topics:
Gun action - Scope - Bolt action - Semi-automatic - Large caliber sniper rifle - Bipod

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Certain design features help modern sniper rifles place the bullet within a minute of arc:

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• Rifles are built to tight tolerances. In particular, the headspace is as small as possible.
• The barrel is precise. The production method is less important. Good barrels' rifling can be cut with a lathe or swaged with a button. Some barrels have metallurgical treatments to reduce their internal strains, and thus the amount they bend or twist with temperature.
• A "free-floating barrel" is often used. The barrel is attached to the rifle at a single point, screwed into the action, not touching the forearm, "front furniture" or sling. This makes the first shot more repeatable since it helps isolate the barrel from outside mechanical and thermal effects.
• The action is affixed carefully to the stock. Often a plastic "bedding" compound is used. It increases the rifles' repeatability by reducing tolerances between the stock and action. Some engineers claim it raises the mechanical resonant frequency of the rifle, reducing the wavelength of resonances, and thus the total error from them.
• Most sniper rifles have heavy barrels to increase the resonant frequency (again) and slow the rate of heating, which reduces thermal distortion of the barrel as more rounds are shot.
• The end of the barrel may be counter-sunk a few millimeters to protect the critical exit-end of the rifling.
• The trigger sears may be polished so the trigger releases crisply. This reduces the shooter's tendency to jerk the trigger, and move the point of aim. A good trigger lets off or 'breaks' cleanly without any 'creep.' It is said to feel like snapping a glass rod.
• A low-mass (often titanium) hammer and pin reduce the time between the trigger pull and the primer ignition. This reduces the distance that a human being's irreducible quiver can move the point of aim.
• There is no correlation between barrel length and accuracy. Military sniper rifles tend to have longer barrels of around 600 mm to allow the cartridge propellant to fully burn and get the fastest bullet velocity for a given charge. Some police sniper rifles have shorter barrels to make them easier to handle. The shorter ranges at which police operate permit lower bullet velocities.