For years, the NATO program on PDWs have focused on weapons designed to meet the PDW requirements, instead of current weapons, such as subcompact carbines. This focus has derailed PDW programs due to budgetary concerns with new weapon systems and their dedicated ammunition. However, the new US small arms RFI could signal a change.
This RFI is looking for what is out there in the carbine and subcompact carbine market. Subcompact carbines such as the Close Quarters Battle Receiver; or AR pistol generally serve the SOF community in the US military. However, subcompacts can satisfy the PDW requirements quite well.
Subcompacts are small and light, which is the main requirement for PDWs, whose users have to carry a weapon while performing their daily jobs of maintenance, commo, etc. An AR subcompact would also ease the training requirements, because they share the same operation and maintenance procedures. An AR subcompact can also share the same ammunition as the M-16/M4 system, or their follow-ons. The AR subcompact shares many parts with its larger carbine sibling, making it cheaper to develop and acquire.
The various piston upper receivers are also available for subcompact AR carbines, so we have piston alternatives.
The many virtues of the subcompact carbine/pistol makes it a politically and militarily viable solution to the PDW requirements. Now if only they can do something about the subcompact's muzzle blasts...