.550" bore dia. is nominal for the 28 ga. I don't think RA was saying it is better than any other "bore match", but that it is a "good" match. After having owned and used one on clays and birds I agree. It is an amazing thing how hard the 3/4 oz. 28 ga. load hits on both.
I'm not the only one to notice that, either. Bob Brister wrote that Neil Oldridge of Remington Arms Co. once told him that there were two mysteries in shotgun ammunition that he could not fully explain. One was why the 28 gauge is so highly efficient for the shot load it throws and the other was why the 12 ga. 3 1/4 - 1 1/4 pigeon load patterns beautifully in almost any barrel.
I know it's not the kind of empirical evidence you like, Miller, but too many people over the years have noticed the same smoke for there not to be fire there somewhere.
Best, SRH
