Im guessing its these
http://forums.airsoftmechanics.com/index.php?topic=11323.0
http://forums.airsoftmechanics.com/index.php?topic=12867.0
Here are some quotes for anyone who cant be arsed to read the lot
"All in all i wouldnt buy any other brand of barrels. I have a madbull black python and quality doesnt come close. I keep the zci in my go to. On a side note i did roll the barrel on a flat percision ground inspection table... it wobbled as much if not less as the madbull barrel(about .010"). I did measure the madbull in the same fasion but this is a review on the ZCI barrel. like i said this wobble is insignificant because the barrel bore is straight. I do recomend these barrels to anybody. I give these barrels my stamp of aproval".
"Grabbed one at random to take some snaps of. The bore finish is actually among the highest I've seen out of a steel barrel, easily the highest I've seen out of a budget steel barrel. Looks like a bead wash sort of. Disadvantage of this is that it makes it easier to see flaws. Nothing major, but you can see where cutting was done for the chamber, crown, retention slots, etc. Crown was also solid. Straightness (of the one) looked good too. I was actually pretty damn surprised by this one to be completely frank".
"1) The above average bore finish is, usually, only on the barrels with the deeper crowns. The ones more or less squared off at the ends don't seem to have it. What they have looks more like what you'd find in a typical promy bore, that sort of odd almost crystal stretch mark pattern. The crowned barrels with the nice bore finish seem to have started with that sort of pattern, but have what looks for all the world like a fine stone wash finish. I have no idea how they applied it.
2) These barrels are, on average, better than the Core barrels in all design, manufacturing, and performance aspects I've thus far measured.
3) The straightness of these barrels is only about on par with your typical entry-level upgrade barrel. That doesn't make them bad, but they're no PDI competitor in that respect".