Has anyone heard or interested in a the RRA-PDS in a pistol caliber set up. No buffer tube, folding stock acceptable, MP5 like handling. Any input ? Pros & cons , possibility of it happening.

If it's a blowback system, it would need more mass than would be available with the short bolt to slow down the action and not beat the gun to death.
If it's gas-op, with the current system, the port it too far forwards for pistol pressures, and if you moved it back, you'd lose the op-rod length and therefore action spring length and bolt travel.
I'm sure it CAN be done, but not with the current style operating system, it would be more proprietary parts.





ETA: the Oly OA-93 style system could probably be more readily adapted to pistol caliber if you moved the gas port in and removed the added mass on top of the carrier.  They're a bit funky looking, but it could work.





I HAVE given it some thought before, as I was thinking of building a bufferless .45 upper similar to my .223/6.8 uppers....

But i went ahead and built a standard DI .45 upper with buffer instead.  For now at least...