The Konstantinov SA-006 experimental assault rifle is historically important because it served as a major rival for the new Kalashnikov A3 (later AK-74) assault rifle during extensive trials of 1968-1973. Starting early 1960s Soviet army began its search for a small-bore, low recoil small arms system to compete with the emerging American M16 rifle and its 5.56mm ammunition. By 1968 several promising new designs were ready for tests. Major rivals in the first round of trials were Kalashnikov A3 assault rifle of the classic design, closely based on the Kalashnikov AKM, and two entirely new rifles with balanced action – the Konstantinov SA-006, designed at Kovrov Machine-building plant, and Korobov TKB-072, designed at TSKIB SOO in Tula.

During the second round of trials in 1969, only the Kalashnikov A-3 fulfilled all requirements, with SA-006 came close second and TKB-072-1 third. Those three were approved for the final round of trials at TSNIITOCHMASH, which took place in early 1970. SA-006 proved to be the best in regards to the effectiveness of fire, having less full automatic dispersion in all shooting positions and scenarios. After review of results, A-3 and SA-006 rifles were approved for field trials, and orders were issued for the manufacture of 100 rifles of each design. In 1970, the Konstantinov SA-006 rifle was also tested against the US M16A1 rifle, and found to be superior to American rival, especially when fired in short bursts from off-hand (standing or kneeling) positions.

Extensive field trials of Kalashnikov A-3 and Konstantinov SA-006 rifles were conducted in the Moscow and Zabaikal military districts and included a broad variety of firing courses, performed by individual soldiers and small units. On average, both 5.45mm rifles performed noticeably better than the standard-issue AKM, with generally similar results. SA-006 had a slight edge over A-3 when fired from off-hand positions, but it also had some specific weak points, inherent to its more complicated design. In regards to combat effectiveness, SA-006 was considered to be about 10% or less good than A-3, but SA-006 was also less durable, much more complicated to maintain and repair in the field, and required much more force to manually cycle the action, especially when clogged with dirt and powder residue after extensive use.

As a result, in 1973 Soviet military selected the Kalashnikov A3 assault rifle as its next primary weapon, and adopted it next year as Kalashnikov AK-74. Development of the balanced action rifles, however, continued through the following decades, and Konstantinov SA-006 assault rifle served as a starting point for the AEK-971 assault rifle.

The Konstantinov SA-006 rifle featured gas-operated, balanced action with dual, counter-moving gas pistons which entered a single T-shaped gas block, located above the barrel, from both sides. Upon discharge, the main gas piston moved rearward, operating bolt carrier with a fairly conventional rotating bolt with dual locking lugs. Forward-moving piston operated the balanced counter-weight, which was located above and around the main piston rod. The main piston rod had a U-shaped cross-section, while balanced weight had an “inverted U” shape. Tandem synchronizing gears are located inside the channel, formed by two operating rods, and engage sets of holes, drilled in both pistons / operating rods to ensure their synchronous opposite movements. A single return spring was mounted above both piston rods and was connected to them. During partial disassembly, the entire operating assembly with bolt carrier, two pistons, return spring, and synchronizing gear caret can be removed as a single unit/subassembly. The receiver was made from stamped steel, with a detachable stamped top cover that featured heavy ribbing. The top cover was assembled with an upper handguard and gas system cover, and detached from the gun as a single unit. The trigger was of conventional, hammer-fired type. A manual safety/fire mode selector was located on the right side of the gun, above the pistol grip. It featured a separate dust cover for the charging handle slot, mounted on the same axis as the safety/fire selector lever. Selector lever had three positions – safe, single shots, and fully automatic. Gun was fitted with wooden furniture (pistol grip, handguards, shoulder stock). Shoulder stock had large cuts on both sides to save weight; the cleaning kit was stored inside the hollow pistol grip. The forward sight was mounted on a base, located near the muzzle; the adjustable rear sight was mounted on the detachable top cover/handguard assembly. Ammunition was fed from box magazines, compatible with its rival, the Kalashnikov A-3, which later became the AK-74.