Over the years I have had barrels from Bullberry, SSK Industries, Virgin Valley Custom Guns and On Target Technologies. In addition I have also had more factory barrels than I care to admit to. In a nut shell the factory barrels shot quite well, but for the most part all of the Custom Barrels shot better.
I had two basically identical barrels in 6mm T/CU. One was made by Virgin Valley Custom Guns and the other by On Target Technologies. Since I had a lot of once fired brass left from the Virgin Valley Custom Guns Barrel I sent some fired cases and sized cases to Mike at On Target Technologies when I had that barrel made. Mike made the chamber to the exact dimensions of the first chamber, and the fired brass from the first barrel fit into Mike's barrel like it was made of it.
The thing Mike did differently was he throated the barrel to the dimensions of the dummy rounds I sent him with an 80gr. Nosler Ballistic Tip seated so the base of the bullet was at the base of the neck of the cartridge case. Not sure if it was the machining, Mike's attention to detail or just the differences in barrels but the On Target Technology Barrel shot a little faster and more accurately.
While not the same cartridge, I have had two different Bullberry Barrels chambered for the 6mm-223. One was a shooter the other not. In fact I had to send the one back to Fred due to a chamber problem, and Fred tried to fix the chamber but was unable to so he made me a totally new barrel no charge. However that was the one that was not a shooter.
The SSK Industries Contender Barrel is a .250 Savage that I currently have (just reaquired it from the buddy that talked me out of it several years ago). This one is a good shooter, equal to most of the factory barrels I have had and better than some. It consistantly prints groups of 1" or less, but I have yet to hit the elusive 1/2" mark (which is my mark for a great barrel).
All in all I think you can have good or bad from any of the barrel makers, just like you can with T/C Factory Barrels. If I were to order a new barrel tomorrow I am quite certain it would be from On Target Technologies.
Larry