Mikecr is right. They should have started with the 25 and gone UP from there. I love the idea of a 26 wssm. A friend of mine improved it and gets 6.5x55 swede ballistics with less powder and it shoots scary, little groups.
I have worked on one 25 wssm thus far and found that while it would get into the mid range 25-06 speeds, it shot much better about 100 fps slower. Deviations were normally pretty good and accuracy from the little Browning pencil barrel was surprisingly good once I let it cool. Once the proper load was found, I could hold 4 inch groups at 650 yards with the Nosler 115 BT. Energy was still enough to kill any deer living.
The 243 wssm has nearly identical case capacity to a regular 243 win except it usually will go slightly faster, have better standard deviations, and wider charge nodes according to the fellows that have them. But I would still rather have a 6br. /ubbthreads/images/graemlins/wink.gif
The 223 wssm is a complete waste of time in anything other than an 8" twist and even then it is VERY hard on barrels.