I would never go as short as 3", but my .357 sig gun has a 5" barrel and will hit 2250 fps. My B&T TP9 has a 5 inch barrel if I remember correctly, and my CMMG 9mm has a 8 inch barrel.

I view the PCC as a niche weapon that is compact enough to go covert but still gives you better accuracy than your pistol and faster hits.

If the barrel is 10 inches then I would go for a 5.56 rifle