therefore possible for accidental discharge to occur as the bolt pushes an unfired cartridge into the chamber, should there be an obstruction in the firing pin channel resulting from poor maintenance or extreme cold. The firearm is operated by a short-stroke gas piston system with a two-position gas regulator. The gas regulator can be set with the help of the rim of a cartridge. Position #1 leaves a gas escape port opened, whereas position #2 closes the gas escape port and directs extra gas to the piston, increasing the recoil velocity of the gas-piston system and is used for resolving reliability issues which arise from fouling in the gas port/action, extreme cold, high altitude, or using under-powered ammunition. The rifle is fed from a detachable curved box magazine with a 10-round capacity and the cartridges are double-stacked in a staggered zigzag pattern. After discharging the last cartridge from the magazine, the bolt carrier and bolt are held back on a bolt catch that is released by pulling the cocking handle to the rear. The rifle's receiver is machined to improve precision by adding torsional strength. Barrel The barrel profile is relatively thin to save weight. Its bore is chrome-lined for increased corrosion resistance and features four right-hand grooves. Originally, the twist rate was 320 mm (1:12.6 in), as it had been designed for use with heavier civilian ammunition. In 1975 the twist rate was increased to the standard 240 mm (1:9.4 in), which reduced the precision with the 7N1 sniper cartridge by 19% but allowed for the use of standard "light" ball steel core LPS Gzh (57-N-323S), as well as its variations (incendiary, tracer, armor-piercing) with acceptable precision. The front part of the barrel features the front sight assembly and a bayonet lug. The muzzle is equipped with a permanently affixed long-slotted flash hider. In order to pass inspections at the factory, these rifles must not produce more than a 0.7 MOA median deviation from the expected point of impact in three 10-shot groups using 7N1 (approximately 3 MOA). Ammunition To enable the desired precision of the SVD, new "sniper" ammunition, designated 7N1, was designed by V. M. Sabelnikov, P. P. Sazonov and V. M. Dvorianinov in 1966 to meet the new standards. 7N1 sniper cartridges should not produce more than 1.24 MOA extreme vertical spread with 240 mm twist rate barrels and no more than 1.04 MOA extreme vertical