I use a flatline...havent used them with the stock barrel.
-don't break with Flatline
-can't think of a weakness, best paint I've ever used.
I usually purchase a box of 2000 Zap balls from Walmart for $40CAN because of the quantity, sometimes a bag of RPS Stingers and RPS Polar Ice during the winter time from the local dealer.
We play at an old army barracks from WWII, with a 4 storey tower included. I purchased a bag of Premiums one weekend and was impressed with them, they fired very accuratley and far out of my barrel compared to the other paint I use. The next weekend, with the Stingers, I could fire to the top of the building with the flatline, but they curved, swayed and took sharp turns to the right or left and sometimes wouldnt fire near the top at all. I emptied out the hopper and put in some of the left over Premiums. They hit the top every time within about 2-3 metres of each other, enough said.
Even though Im spending more on paint now, its well worth it. I would recommend it to anyone with a flatline on their 98, since I havent fired it through anything else. I hear a lot about flatline breaking balls and requiring high-end paint, but mine never broke one ball even the Zap from Walmart, so...the balls dont break inside the barrel, at least inside of mine they dont.
I know there is better paint out there, but Im giving it a 10 because its the best Ive used in the 8 months or so Ive been playing. Accuarate and affordable.