The currently assessed performance (BC's) for the Berger 300 grain Hybrid is derived from 1000 yard testing, not 600 yards. The originally assessed BC's for the Gen 1 version of this bullet were done at 600 and were inaccurate (something like .890/.450 G1/G7). Since then, I only test .338's at 1000 yards, and the current BC's have been measured repeatedly in several tests at 1000.
Here is my full reply to the Snipers Hide thread regarding the test results:
"As some of you may remember, when this bullet (the .338 cal 300 grain hybrid) was first released (Gen 1), I had assessed inaccurate performance (.455/.889, G7/G1) based on testing at 600 yards. Further testing at 1000 yards indicated the currently assessed performance of .418/.819, G7/G7.
The cause for the discrepancy in my results is not attributed to BC decay at 1000 yards vs 600 yards, but rather testing at 600 yards is simply too error prone to work with larger caliber, high BC bullets. In other words, normal uncertainties in MV, range, atmospheric variables etc result in unacceptable % uncertainties in measured BC. When measuring the BC of a high BC bullet, the test has to be conducted at longer range in order to manage the measurement uncertainty."