Look, I know many of you might disagree with my comments regarding the Flatline, but this was my experience with that barrel.
I bought this barrel because my friend's A5 had a Flatline and I loved the performance of his gun. I used it a few times and I know a Flatline for my X7 Phenom will be a great addition.
The first and only time I used my Flatline... I was frustrated. I tried to tune my gun and I just never could do it. From my frustrations, I borrowed my friends Apex barrel. I was impressed with the performance of the barrel, but I hated how it looked. Then the Apex 2 came out and I had to get that instead. So, I sold my Flatline and for the price I sold it, I bought the Apex 2 Barrel. The Apex 2 was pretty much idiot proof. I set it and it worked. Didn't really have to tune it. I'm happy with my choice and I'm sticking to my Apex 2.
I spent more than $80 at the time when I bought my Flatline. I wish I would have just waited and gotten the Apex 2. I would have saved $30.
I love Tippmann... I love the products they make. But, I just didn't quite like the performance of the X7 Flatline. This barrel is super picky with paint and I can't always afford to get the top quality paintball when I play, so I believe my decision is correct.