98 with Flatline Barrel is very accurate as is the A-5 version, Pro-Carbine which is as durable and reliable as any Tippmann even with a Flatline Barrel installed.
I currently own an A-5 with a Response Trigger, Venturi Bolt, Expansion Chamber, and Flatline Barrel. I also have a 98 Custom with Flatline barrel, Venturi Bolt, Expansion Chamber, and CAR-15 Stock.
Any slightly harder smaller caliber paintballs such as Diablo Blaze, RPS El Tigre, or RPS All Stars. RPS Marballizers are a bit snug of a fit for the barrel.
This is an excellent accessory for the Tippmann A-5, simply elevating the effectiveness of this rapid fire gun to incredible heights. It is excellent for distance support firing paintballs en masse while equally suited for choice sniping shots. Combine the Flatline Barrel with the Cyclone feed System and you are capable of putting out quick accurate shots of an unprecedented caliber. Using the paintballs listed above I've accurately hit head sized targets at distances over 100 ft. repeatedly.
Many a complaint for the Flatline system has always been their pentient for ball breaking. I personally have never encountered any problems of the sort with either of my Flatline Barrels while using the ammo I do. Keeping the barrel straight is another factor for effective game play and it is simply operator failure that is to blame for inaccuracy due to this.
I have had NO problems as of yet with this barrel or the barrel system for the matter. My experiences with Tippmann products in general has been impeccable, as have the experiences of many of my friends. Until the day Tippmann makes a faulty product I will stand by there tight-@$$ markers and unique line of upgrades.
If you've got an A-5 and can't take the pressure of close quarters, or like myself just love to rain down paintballs from grand distances the A-5 Flatline barrel will suit you wonderfully. If you've never used a Flatline barrel before it takes a bit of getting used to, but that time spent is well worth the enjoyment of consistent long range eliminations in the end. Hell yah!