The Bulkin AB-46 assault rifle, also known as the Bulkin TKB-415 assault rifle (in Russian: Автомат Булкина АБ-46 / ТКБ-415) was an experimental assault rifle that competed against the Kalashnikov AK-46 and AK-47 rifles in Soviet assault rifle trials of 1947. Chambered for the new 7.62x41mm M1943 intermediate cartridge (an experimental predecessor for the famous 7.62x39mm M1943 round adopted in 1949), it was designed by Alexey Bulkin, who was a staff firearms designer at the TsKB-14 weapons design bureau in Tula.
The first version of the Bulkin TKB-415 assault rifle was tested in mid-1947 against a number of other designs, including the Kalashnikov AK-46, Korobov TKB-408 and several other experimental rifles in the same caliber. Since neither weapon performed satisfactory, the trials commission ordered three best performing weapons (by Bulkin, Dementiev and Kalashnikov) to be resubmitted for next stage of trials, scheduled for late 1947. All three designers received lists of recommendations and suggested upgrades to their respective weapons, including one common suggestion to shorten barrels down to 40 cm. Bulkin also received recommendations to redesign the safety / fire selector, and make his gun more durable and reliable.
Final version of the TKB-415 rifle was tested against the competing designs from Kalashnikov and Dementiev in December of 1947. Both rifles, submitted by Bulkin (one with a fixed stock and another with a folding stock) performed rather unsatisfactory, with very poor reliability and durability. In fact, both TKB-415 rifles failed completely in the endurance trials, and were out of action in less than 7,000 rounds each, while full endurance trials required 15,000 rounds to be fired through every gun. The only one advantage Bulkin rifle had over the much durable and reliable Kalashnikov AK-47 was its better (smaller) dispersion in automatic firing. Otherwise the gun was a remarkable failure. As such, in the official trials report, issued in the January of 1948, trials commission recommended to go forward with the AK-47 and to abandon further development of the Bulkin and Dementiew rifles.
Despite that, during the 1948 Bulkin produced a slightly improved version of his rifle, known as the TKB-452, which had a slightly redesigned gas system. However, it did not help much to improve inherent flaws of his design, including poorly distributed weights in the bolt group and inefficient bolt to bolt carrier interface which had poor leverage for unlocking and produced too much internal friction.
The Bulkin AB-46 / TKB-415 assault rifle is a gas operated, selective fired weapon. It uses long stroke gas system with the piston located above the barrel. Bolt has two lugs that lock into the front trunnion of the stamped steel receiver. Bolt rotation is ensured by a cross pin which in inserted into the bolt carrier and slides across the cam surface on the bolt shank. Early version of the TKB-415 had a non-reciprocating folding bolt handle and small safety / selector lever of the right side of the pistol grip. Later version of the same gun featured cocking handle permanently attached to the bolt carrier, and a safety/fire selector located on the left side of the grip. Both versions were equipped with the muzzle brake / compensator, which proved to be inefficient in trials.
Finally, it is interesting to note that the Kalashnikov AK-47 in several important design respects bears more similarities to the Bulkin TKB-415 rather than to the Kalashnikov AK-46. These similarities include overall layout of the U-shaped receiver with detachable top cover, long-stroke gas system. However, Kalashnikov used a much better and indigenous design of the bolt group, which resulted in much better reliability and durability in all conditions. Since all mentioned designers worked on their rifles on the government-paid time and resources, it was a common and officially encouraged practice to use others’ ideas when the national interests were concerned.
Specifications for the late TKB-415 rifle with the fixed stock: