Military sniper rifles used by different military units. Along with main requirements for accuracy and sufficient effective range, military use commands some other: military sniper rifle must not be too heavy, because sniper usually must carry it for the long hours, with ammunition and other stuff. Also, military sniper rifle must be extremely reliable in any weather and climatic conditions and could withstand hundreds of rounds fired without cleaning and maintenance and without any loss of accuracy. Third, military sniper rifle must be easy to fieldstrip and easy to repair in field conditions. Also, military sniper rifle often must have backup iron sights, in case of telescope breackage. Another requrement is that military sniper rifle must use military ammunition, conforming to international war threaties and generally available to the troops. In most cases, military sniper rifle use variants of the standart caliber army cartridges (such as 7.62mm NATO or 7.62x54mm R), specially developed for sniping. Effective range for the standart-caliber sniper rifles against the single human-sized target may be estimated as 700-800 meters for first-shot kills. To extend effective range beyond 1000 meters, often used sniper rifles, designed to fire more powerful ammunition, such as .300 Winchester magnum (7.62x67mm) or .338 Lapua magnum (8.6x70mm).