How old is the gun? Is it used a lot? If you're good at disassembling stuff and putting it back together then you may be able to fix it. If not then I would suggest buying a few one as thier not expensive. There are a few reasons why the darts may not be foreign far. The spring may be worn down. If that's the case the spring can be replaced. The barrel or piston may be congested. Look inside to make sure nothing is blocking the piston. The darts may be to blame. Check your darts, if they are ripped this would cause them not to go far or if they are the wrong darts they won't fire correctly. Make sure the darts are the same kind as the darts that came with the gun and that they don't have rips.