I need help please.

The arc in the Flatline barrel gives the advantage of greater distance.  You'll also notice on the inside of the barrel following the arc the barrel looks scuffed.  The barrel was designed this way.  When the paintball is fired through the barrel, it is forced to make contact with the top of the barrel causing backspin.  This backspin causes the paintball to travel in a flat trajectory when leaving the barrel.

Another question that hasn't been fielded is what kind of paint are you using?  Flatline barrels perform better when using a small to medium bore paint like the old Marbs or Evil.  If you you're using large bore paint, you will likely not get the desired effects with your barrel.  When you use the right sized paintball with the correct air velocity, you will get the results  you expect from the barrel.

To get the best performance out of your Flatline you should:

• Use medium to small bore paint.
• Be chronoed at between 260 and 270 fps.
• Hold the marker vertical to the ground with no tilt to the left or right.
  

I like the J&J ceramic and the Lapco Bigshot.  Both are reasonably priced, very nice after-market barrels.  Neither is anything fancy, but both are probably as high-tech as most people will ever need to go on a Tippmann.