Thanks Darryl, I'll email you about the case. Sounds like the sure fire way to go.
The JGS site has a 338/416 Brooks reamer, is this the one you have used?
With the 300gn Sierra what OAL do you use and how far off the lands are they? All the Weatherbys have quite a jump so I wonder if accuracy is being comprimised a bit to keep the PSI from spiking.
I loaded some .416 Wby 400gn Barnes XLC's to .030" off the lands and groups went from under .750" to 1.75". The bullet had to be seated out quite a ways so powder charge may have needed to be adjusted is all.
I never checked though, just figured they might all shoot in the same hole so I tried it once. Same thing with the 400 Swift also. Fun fun fun, $$$ testing is. Brent