At the risk of splitting hairs and picking nits, effective range (exterior ballistics) is a factor of barrel length. Accuracy is impacted by site radius.
In general, a longer barrel will have a greater effective range than a shorter barrel because of the higher velocities achieved due to more complete buring of the propellent.
In short, if you want to shoot [i]farther[/i], get a longer barrel. If you want more [i]accuracy[/i], get a longer site radius or a scope.