Check out FLASC Paintball; they've got some really affordable barrels and kit options that will allow you to create any length, porting, bore and APEX ready tips to let you install on and off your barrel on the fly. Sizing your paint to your barrel's bore will be the best increase to "accuracy" you can have.
There's a pic below to give you an idea.
If you've got any questions or need any assistance, don't hesitate to give me a shout! I love my FLASC barrel kit, and it would be a HUGE improvement over the stock barrel option.