Read again: efficient.
Efficient isn’t quite as critical with an ‘06 case as it is with stuff that fits in an AR15. It’s just a generality of load physics that explains why larger bore to case ratios often show more initial performance with less powder/pressure. Less efficiency doesn’t mean something can’t be better for a given purpose. It just means there’s sometimes a trade off. I’d actually like to play with a fast twist, trimmed 6x6.8 for giggles.....but it’d likely need >20” of barrel to get somewhere good.
