What do you expect us to say? Should we magically know what your problem is when your first post is just "Longshot sucks guys!!!"
Sorry I'm just in the school of thought that the people here would be mature and give constructive criticism instead of flat out insults.
Besides that I think the point of the 2-3 shots per second is probably the problem. From playing paintball a lot you get ball chops which is when the ball is half way in and out of the breech. This is probably what is happening with the longshot because the spring takes time to put the dart up in the chamber. Taking a tiny bit longer to re-cock the gun this might solve the problem.
Also, check some writeups, and check what you have taken out. Alot of people I know sometimes take out EVERYTHING that looks a little like it could hinder performance, even if it necessary.