This new cartridge is designed by a Russian company called Techcrim – the co-developer of the .366 TKM and 9.6x53mm Lancaster cartridges. The .345 TK cartridge is based on the 5.45x39mm case that has been shortened to 22mm (.866″) and loaded with rather odd .345 caliber (8.76mm) bullets.
Just like in the case of the .366 TKM and 9.6x53mm Lancaster, the .345 TK was also specially developed and certified as a smoothbore cartridge. It is supposed to be used in oval bore (a.k.a. Lancaster) or half rifled barrels. The Lancaster rifling has an oval cross-section of the bore that has been twisted to impart spin to the projectile. The absence of distinct lands and grooves qualifies it as smoothbore in Russia. In case of the half rifled barrels, the bore starts smooth with the riflings present only at the last 5-6″ of the barrel. In Russia, this is legally considered a smoothbore barrel with a built-in rifled choke. The reason why they try to develop cartridges and guns that would be legally considered smoothbore (still providing close to rifled performance) is that smoothbore firearms are much easier to obtain in Russia.
With the overall length of the .345 TK cartridge identical to 9x19mm, it will be possible to easily re-barrel PCCs (such as the Saiga-9, Kurbatov Arms R-701 etc.) and convert them to .345 TK guns. According to Kalashnikov Gun Magazine, the .345 TK will be available with a subsonic 147-grain (9.5 gram) FMJ bullets as well as 115-grain (7.5 gram) hollow point and FMJ bullets.
You have probably noticed something unusual in these images. Note the thickness of the case at the mouth. It seems like the 5.45x39mm cartridge cases have been simply chopped to 22mm and loaded with bullets without trimming the case wall thickness. Probably, these are images of prototype cartridges, otherwise, I am quite skeptical about the obturation of the chamber with such a thick case mouth. Compare it to your standard 9mm ammo – it is at least twice as thick.
Images from www.kalashnikov.ru