I'm not familiar with the Tesro builds but the CZ 455/457 action is capable of excellent performance with a little TLC. A guy on RFC had a full benchrest style 455 built with a Benchmark barrel and he pulled off a sub 0.100" 5 shot group at 100 yards with it. The thing is, the rifles can be built to perform better than what a lot of ammo available to us is capable of delivering. That said, it's not usually as simple as slapping in a pre-fit barrel to get such a capable rifle. I'm sure more often than not, IBI pre-fit builds will satisfy the precision requirements of PRS sports. Is it getting the best out the rifle/barrel? Maybe not, something might be left on the table. To get the best out of a CZ the barrel should be custom fit to each receiver and secured with a more solid/stress free mounting than the set screws like "gluing in" the barrel with green Loctite. Their chambering is also likely not optimized for accuracy, but for function. Can't have customer complaints about trying to extract a live round but leaving the bullet stuck in the chamber, after all. The engraving necessary for best accuracy necessitates that any chambered round must be fired, trying to extract a live round not advised. Of course a balance can be struck where there is sufficient engraving to provide excellent accuracy while also allowing for live round extraction, hard to say where that fine line lies though and where a pre-fit barrel compares to it. I'm interested to see what a full custom build with an IBI barrel can do, what I've seen others post with pre-fits is encouraging.