For information and reviews on tightbore barrels see:
http://www.arniesairsoft.co.uk/forum...owtopic=146196
http://www.madbullairsoft.com/images...l%20Report.pdf
Translate out of Google:
http://www.6millimeter.info/joomla/i...=150&Itemid=42
And:
http://www.airsoftforum.com/board/Pr...1-t124688.html
http://www.airsoftretreat.com/forums...?topic=56248.0
The German guy says Madbull and Prometheus are the best, TCF says EdGI is the best.
I use Prometheus and Madbull barrels and have gotten excellent results with them.
If you were to buy any of the top brands, Prometheus, Madbull, PDI, Systema, CA or EdGI they would all shoot very close to one another.