I may be wrong, but aren't low velocity rounds undesirable for longer ranges compared to higher higher velocity rounds?
Isn't the idea of a PDW to be a small carbine to replace the pistol with something that can shoot farther than a pistol?
I have read reviews of 2-3 inch groups at 100 yards with the jr carbine - I don't know about you but I can achieve that at 25 yards with my 1911 but at 100y most pistol shooters would be lucky to hit a target, myself included. I am set up to reload 45acp and have a dozen 1911 mags so for me its a no brainer.