Barrels aren't the be-all, end-all of range. Your hopup will have more of an effect on that than the barrel will. Those who have seen, tried, and been on the receiving end of my MP5 have been amazed at both its range and accuracy, especially considering its velocity (formerly 330 fps, now 350).
And shit, last weekend I was getting 100 foot range kills outdoors using my pistol (Glock 17). A longer barrel will give you a bit of extra range, but it's not everything.