DF,
After firing a few 26 Nosler cases in the Nosler rifle, I measured the H20 capacity with a 129-grain Hornady Spire Point seated to the front of the cannelure, and it went exactly 90 grains. (This is a more accurate way to measure useful powder room than just filling a case to overflowing.) In comparison, a fired Winchester-brand .264 Winchester Magnum case held 80.6 grains with the same bullet, seated the same way. According to the 4-to-1 Rule, this works out to a 4.8% velocity advantage for the 26.
Also tried some rounds in three different rifles chambered for .30-06 legth belted magnums, and while not every round fed perfectly I doubt it would be hard to tweak either a CRF of push-feed action so it would work well.
