Tests have shown very good flatness feathered piercing bullets, but the accuracy of a few opportunistic ordinary ammunition.
Automatic AO-27 construction DI Shiryaev is part of the most experienced complex "instrument — cartridge swept by a bullet, "was developed in the NII-61 (later — TsNIITochmash) since 1960. By that time, was completed a number of research projects aimed at increasing the effectiveness of the AK-47 fired from unbalanced positions (standing and kneeling). At Finally, it was found that the more applicable method to solve this tasks is to reduce the recoil momentum. To keep with all this and even increment blank range, it was necessary to reduce the gauge.
It earlier reached a similar conclusion in the United States, where they were developed cartridge and 5.56-mm machine gun. Building the Russian analogue of such holder was initiated by the control cartridge direction NII-61 VM Sabelnikova. As candidates Department of aviation armament NII-61 was proposed in parallel to check the possibility of using for the same purpose cartridge with arrow-piercing bullet. Hope for success gave what at that time had already been developed swept Russian armor-piercing discarding sabot projectiles with a 100-mm anti-tank gun T-12 "Rapier". Construction of such ammunition, i.e. cartridge with a feathered arrow-piercing bullet and a detachable two-sector leading pan-type gun "machine" was designed in 1960 and is protected by copyright certificate N 22527 with a value of 1 June 1960.
The creators of this invention are the VP Dirt, PA Fadeev, AG Shipunov and DI Shiryaev. Patron was given the code OPS (feathered Subcaliber shooting). Automatic AO-27 for this ammunition was first developed in 1961. Ammunition and OPS automatic SA-27 to it are first in the world shooting complex kind. Later this idea of trying to translate the Americans, but their long-standing efforts in this direction have not met with success. Automation AB-27 gas operated type with removal of powder gases through a hole in the side wall of the trunk. As the barrel blanks used regular trunks of 7.62 mm, which were made in the regular rifling profile, but more gentle. The rotation of the bullet sectors contributed to accurately separate pallets, leading the bullet down the barrel. Apart from this, the rotation of aerodynamically stabilized bullets happened averaging eccentricity forces acting on it, and, as it should, reducing the spread of hits. Shutter — swivel, with 2 locking projections.
The barrel valve is structurally made together with the stem ending in a gas piston. In the hollow gas piston rod is revertible spring. The firing mechanism striker type with longish course (in fact equal to move the gate) drummer. Made it to the growth cycle time of the automation to reduce the rate of fire. The trigger is a simple type, consisting of a trigger, sear pivot, self-timer and uncoupler. Fuse-translator flag type is placed on the trigger guard behind the trigger hooks + com by analogy with self-loading rifles SVT. Sights consist of the rear sight and front sight.
In the first case the machine was diopter rear sight and front sight was placed in a gas chamber. In developing complex military advice sight was replaced by the ordinary adjustable sector, and adjustable front sight moved to the muzzle. Shooting done with the so called front sear, ie with the movable parts in the front position. According to the reports on tests of the complex of step head designer advantage of it compared with the AK-47 was overwhelming. Namely, machine-blank range is 530 meters, compared to 356 AK-47 rifle and 437.
With all of this recoil momenta were 0.5 in AO-27, 0.78 in the AK-47 and 1.24 kg at the rifle. When shooting at a distance of 1000 m altitude trajectories were respectively 3, 6 and 10.5 meters. Huge initial velocity of the bullet cartridge OPS (1,060 m / s) and transverse load given automaton AO-27, a significant advantage in the penetration of bottlenecking as trench parapet. Significantly the least was the dispersion of bullets machine AO-27 compared with an AK-47 when shooting small bursts from a standing position. But due to a weak stopping power and the highest price of the cartridge topic has been left in the category of research.
Properties machine AO-27 and OPS cartridge:
Weight of the machine with empty magazine, kg 3.2
Length of machine mm 893
Barrel length 415 mm
The number of cartridges, pcs 30
Rate of fire, rds / min 700
Caliber trunk/ Bullets, 7.62 mm / 3
Weight cartridge, 10.5 g
Bullet weight, g 2.4
Cartridge length, mm 63
Slug length, 55 mm
The greatest pressure propellant gas, kg / mm 2700
The initial velocity, m / s 1060