RA, Gamebore 7's--being British--are like our 7 1/2's. Gamebore 6's are slightly larger than our 7's. About 6 2/3.
Tut, I use Brit 6's on pheasants, although almost always something larger in the tight barrel. Either those or 7's are pretty much all I've used on prairie grouse (early season) when I've hunted them. I have some RST 7's in 16ga, but have not tried them on pheasants yet. Back when I had an article assignment that I knew would involve the opportunity to shoot a lot of preserve pheasants, I loaded up a bunch of 3/4 oz 7's for my 28ga, choked IC/M. (Essentially same pellet count as an ounce of 6's.) After flat missing the first bird I shot at, I bagged 27 straight, including a couple true doubles. But I'll quickly add that I think I would have lost at least a couple of those birds had they been wild ones. Needed some good dog work to put them in the bag.
