I'm not sure about the internal mechanics of the longshot but if they are anything like my two larger guns you'll have to take the gun completely apart and take out the bolt that moves back and forth that holds each dart into place. It has a little peg in the center of it that inserts into each dart, you need a long drill bit that will reach through the front or back of the tube to drill out that peg and hollow it out...
look up longshot cs-6 mods on youtube and you should find a few video tutorials explaining the process.