Just got an email ad from Winchester on this new cartridge. It doesn't say much about it, but if any writer has info, what is different about it compared to the .270 WSM?
I'm not a writer but I hope this helps you with specifics on the two rounds.
Every dimension on the 6.8 Western case is identical to the 270 WSM case, except the "linear" ones. The distance from base to shoulder, base to shoulder-neck junction, and case OAL, are all reduced by .080", resulting in slightly less case capacity for the 6.8 Western. The necks are the same length (.2765"). All the other angles and diameters are the same. The 6.8 Western should fit right into the chamber of the .270WSM, with just .080" "excess headspace."
As to the overall cartridge, the Max OAL spec'ed for the 6.8 Western is 2.955", versus 2.860" for the 270 WSM, so you'd see 0.175" more of the bullet hanging out the neck of the 6.8W if the same bullet were loaded to max OAL in both cartridges, which would tend to make up, some, but not all, the capacity lost by shoving the shoulder back almost a tenth of an inch. The .270WSM would still be slightly more capacious.
The big difference is the spec'ed twist, 8" vs 10", and its ability to stabilize longer, better BC bullets.
IMO If everything else about the rifle was identical, the .270WSM would be damn near identical to the 6.8 Western, probably slightly "better", to the extent a few more grains capacity is "better."
Hope this helps,
Rex
