How do I improve my Spyder TL-X?

I have a Spyder TL-X with a 16" custom sniper barrel and a combat stock attached. I have not yet received this items but they will soon be put on my gun. Is this a somewhat good gun and what are some crucial attachments I should buy to improve my guns performance? It was pretty inaccurate so I bought a barrel that is 4" longer so I hope this will fix that problem. Any other tips please respond and if you have a gun, let me know as well as its attachments.