I'll tell you right now.
If you think a sniper rifle will be an advantage in any way. Stop and just shake your head.
Like mentioned before, its expensive as hell just to make one gamable, and thats just to get the thing shooting marginally more accurately, and a bit more further than your conventional upgraded AEG.
Start playing with a regular gun, and once you feel ready to do so, spend the time and money in building a quality airsoft sniper rifle.