The PRC's 5.8x42mm is reported to give similiar ballistics to the 5.56x45mm M855.
The most commonly seen weapons chambered for the new cartridge are bullpup Type 95 series, arranged vaguely like a Valmet M82 crossed with the FA MAS. However, given the appearance of the non-bullpup variant, the Type 87, I suspect that the base mechanism is that of the 7.62x39mm Type 68 and 81 rifles.