I use Diablo Midnights,
They may be a little large, but their thich shells dont easily break.
Very accurate, can outshoot my friend's Empire Twister barrel.
If there's paint in the barrel it screws up the trajectory.
I love the rifling, it makes it shoot a tighter group more consistently.
I tested it against the stock Tippman 98 barrel and the Stealth shot a 2 in. group at 20 yds while the stock barrel shot a 5 in vertical line at 20 yds. (out of 5 shots)
The only weakness that I could find was that if there is any paint in the barrel, the balls will start curving really bad.
I found this out one game, then realized i had been shot in the barrel and that there was some paint in the last inch of the barrel. I grabbed a squeegie and cleaned it out and it shot just like it was new again.
Great barrel, If I had the choice to do it over again, i would have boughten the 13" instead. For me the 16" is just too long, but at 13" it is perfect.
I give it a 9 only because of what happened to the ball's trajectory when there was paint in the bore.