It's not just the twist. It's a whole bunch of stuff. The reamer geometry and case shape and length (and width) of the throat on SAAMI spec reamers, along with COL. The WSM was not designed to shoot ultra-long projectiles with high BC and high SD. Sure, you can cram them into the case, but the SAAMI reamers used for factory rifles and standard magazine length were designed to maximize performance for bullets 130-150gr.
This new cartridge uses a very similar case, but seeks to correct the flaws in the platform. It has a faster twist, longer (and narrower) free-bore, shallower leade angle (for high BC bullets), and most importantly, the max COL is 2.955", so standard magazines will allow for long bullets to be seated long, into a target-leade-taper.
Not to mention nomenclature dysfunction RE: ammo. (See 7mm Rem Express)
As for case capacity reduction?
See that as a plus.
More efficient/less intrusion given applicable long bullets.
Maybe 3 grn less(water)...?
Call it 63 grn/.270 WCF < 69 grn/6.8 W < 72 grn/.270 WSM... for a 150 gr. bullet.
So, one 3 grn jump over a .270 AI.
For 150-175 gr. loads... for me...?
Ideal.
Already budgeting for a M70 EW/SS (24" Bbl.) in 6.8 WESTERN.
8>)
GR
