The best 20 inch paintball barrel?

The optimal size for paintball barrels is roughly 10-14 inches. Anything less tends to release the ball before it has a chance to accelerate. Anything more can use up too much gas, cause inaccuracy if not held completely still. A good "sniper" could use a 16-18 inch barrel, but ONLY if it is held still, with a bi-pod, in the prone position. Trying to run around with a long barrel (16-21 inches) is not only difficult to maneuver, but is actually less accurate when moving, or standing and shooting.