The Kubynov KB-2 is a prototype Russian assault rifle.
The Russian government was looking for an assault rifle to replace their SKS, and as such, the KB-2 was trialed against a few other designs, with designs by Kalashnikov, Tokarev, Bulkin, Shpagin, Korobov and Simonov. However, all lost out to the Kalashnikov design. The KB-2 did not fare well during the tests and was not selected.
The KB-2 used gas-operation, similar to most other designs, but in all other regards was just a standard assault rifle.
The KB-2 fired the 7.62x41mm round, similar to the more famous 7.62x39mm round.
The KB-2 had two versions, which were very similar in terms of apperance.