The Korobov TKB-072 and TKB-072-1 experimental assault rifle (USSR)

The Korobov TKB-072 experimental assault rifle was developed by a talented Russian gun designer German Korobov, who worked at the Central Design Bureau for Hunting and Sporting Arms (TsKIBSOO) in the city of Tula. Work on this rifle started in 1967 as a part of a large R&D program aimed at the development of the new small-caliber assault rifle, intended to compete with the 5.56mm M16A1 rifle, recently adopted by the US Armed forces. At the time the new soviet cartridge was known as the 5.6x39mm MZhV-13 (МЖВ-13); its nominal caliber was changed to “5.45mm” in 1973, shortly before its adoption.

Korobov TKB-072 experimental assault rifle, from Tula Arms Museum collection

Of all rifles submitted to the first test in 1967, the Korobov TKB-072 was probably of the most unusual construction. Besides its gas-operated, balanced action, it used a vertically tilting bolt with two frontal locking lugs. It also had a separate U-shaped rammer/extractor of a rather intricate design, attached to the bolt and swinging up and down below its body during the reciprocal motion of the bolt group. During the opening movement of the bolt group the rammer/extractor remained in horizontal position, holding the fired case by its extraction groove. At the end of the rearward cycle, forward end of the rammer/extractor swung down, directing the fired case into the ejection chute below. During the forward movement of the bolt the rammer/extractor remained in its lowered position and pushed the fresh cartridge from the magazine and into the chamber. At the end of the closing bolt stroke the rammer/extractor swung up to engage the extraction grove of a chambered round by its frontal claws. The TKB-072 rifle had a four position safety-selector, with settings for safe, single shots, low rate of fire (about 500 rounds/minute, from firing from supported position), and high rate of fire (about 2000 rounds/minute, for firing short bursts from off-hand position). A low rate of fire was achieved by a fly-wheel delay mechanism, built into the trigger unit. Finally, this gun has one of the most unusual ejection systems ever made; fired cases were ejected downward (base first) through the special chute, which protruded below the receiver, between the pistol grip and the trigger. Most probably it was done to make firing from inside of the Armored Personnel Carriers (BTR or BMP) more convenient, and avoid showering shooters’ comrades with hot fired cases.

Korobov TKB-072 experimental assault rifle, from Tula Arms Museum collection. The arrow shows direction of ejection of fired cases

Despite rather good performance dispersion-wise, the trial commission recommended the use of only one fixed rate of fire instead of two. Also, its unusual feed and ejection system resulted in an excessive number of jams and stoppages, so it had to be simplified too.

As a result, Korobov soon delivered the TKB-072-1 rifle, which had only one, moderately fast rate of fire and a traditional ejection system through the opening on the right side of the receiver top cover. It retained the swinging rammer/extractor, but added an ejector to   Both versions featured partially exposed “balancing” gas piston and U-shaped action rods, which reciprocated forth and back between the gas block and front sight base.

Korobov TKB-072-1 experimental assault rifle, from Tula Arms Museum collection

The improved Korobov TKB-072-1 assault rifle was tested in 1968 and 1969, but the results were not inspiring, as it was still prone to parts breakages, had insufficient reliability under harsh environmental conditions, and required too much time and effort to clean its intricate internals. As a consequence, it was rejected by the military testers and the final round of trials was conducted between two other contenders – the Konstantinov SA-006 rifle and the Kalashnikov A-3 rifle, which eventually won the trials and was adopted as the AK-74.

Korobov TKB-072-1 experimental assault rifle. Disassembled photo from trials report. The swinging rammer/extractor is clearly visible below the bolt.

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