I am getting in on this thread late, too.
I went round and round with Bart over this issue when he first wrote this on rec.guns. Now, you have to understand that Bart was a big time competitor in his day. He came into his own when the 308 started taking over in Highpower Match. Ten years later, the 223 was dominating.
Some gun writer somewhere along the line came up with the theory that short powder columns rendered more "inherent" accuracy and a bunch of people jumped on the band wagon. After all, the bench rest guys were switching over in droves to the PPC cartridges during the same period. In reality, short, fat powder columns tend to be more efficient, but there is no evidence that short powder columns are more inherently accurate. I found this out when I saw a Kenny Jarrett 30-06 sporter put three round of factory ammo into a bug hole at 100 yards.
My theory is that the 308 took over from the 30-06 in Highpower Match because of less recoil. The lower the recoil, the less strain on the shooter and the longer the shooter is able to shoot without stress. It does not hurt that the rifle for the 308 Win tends to be lighter, either, since Highpower Match shooters have to hold the darned thing up. And IMO, this is the same reason that the 223 took over from the 308 in Highpower Match.
The military switched to 308 for the express purpose of supporting the design of short recoil machine guns. In reality, the decision had nothing to do with logistics and very little to do with ballistics, since there was not a lot of ballistic difference in the T48,308 Win) round and the .30 Caliber,30-06) round.
There is something to be said for short actions being stiffer, but I am sure it is overblown. A long action single shot with a solid bottom is every bit as stiff, if not stiffer, than a short action repeater. And if stiffness was all it was cracked up to be, how did the French win all those military matches with Model 36 actions which are rear-lugged, not to mention all those accurate Remington 788s.
There are so many variables that contribute to accuracy, that I think ammo is just a small part. You can have the best ammo in the world, and if your muzzle is worn out from poor cleaning technique, that fine ammo will produce a pattern instead of a group. Conversely, you can have the tightest tolerance rifle, and crappy ammo won't shoot worth a flip. It's the total system that makes for accuracy.
Dang! I'm getting writers' cramp!