After the decision to create a new family of infantry weapons for the then-new intermediate 7.62x41mm obr.1943 cartridge (the precursor to 7.62×39), Soviet designers were tasked with creating new kinds of weapons in this chambering, including machine guns, selfloading rifles, assault rifles, and bolt-action carbines. This last category was apparently given a low priority, as it was only after the war had ended that any development in this area becomes evident. By this time, the 7.62x41mm cartridge had been replaced by the now-familiar 7.62x39mm round, which had a slightly shorter neck, longer bullet ogive, and steel bullet core.
The weapons were intended as inexpensive rifles for rear-echelon troops, but the semiautomatic SKS carbines were apparently cost-competitive, and production never began for any of the intermediate caliber carbines.
All the weapons apparently had 10-round fixed magazines, fed from stripper clips. Beyond that, the requirements are unknown. Even Russian firearms expert Max Popenker does not know how many designers worked on the project, but there were apparently three different patterns of weapon, two very similar Mosin-Nagant-derived weapons, The KB-P400 from Degtyarev, the ISS-11P-47 from Simonov, and a third Mauser-derived design from Tokarev.
Thanks to Maxim Popenker for the information, and his help ensuring technical accuracy. Also thanks to Retiv for his help translating.