I've used WGP Practice Paint and Stingers, both have worked well.
Strengths:
Durable
Accurate
Quiet
Weaknesses:
Price
Review:
I bought this barrel knowing that I would be keeping my A-5 for a little longer, and it has done very well. It has very noticeably increase my accuracy, and made my gun slightly quieter. I have used only $30-$35 paint through this thing, and it works very well. I can hit what I want to hit at a reasonable distance. The price is a minor setback, as I don't like to spend money. However this is a good upgrade for any gun, and is worth the money.
Conclusion:
If you don't have enough money for a kit, and want a good, cheap barrel that will satisfy your paintball needs, this is definetely the barrel to get.
