PDWs...and other small arms.

[stanc]

An improved 7.62x25 Tokarev, 9x25 Dillon, or 6.5 CBJ would fit the bill in that Magpul Folding Gun.

Much more projectile mass than 5.7x28, higher velocity, low recoil, effective range from 200-300m.

7.62x25 Tokarev, loaded with a spitzer bullet, yes. (Assuming that the COAL allows grip dimensions viable for use by soldiers with smaller hands.)

6.5x25 CBJ (below) and 9x25 Dillon are incompatible with streamlined, spitzer bullets, so I question if effective range would be even 200 meters.