1 oz. is a lot to stuff down a .550" hole.

Much like the extra 1/8 oz. in a 1 oz. 20 vs. 7/8's, I'm guessing most of the extra shot goes someplace other than the traditional 30" circle.

Relying on the fringe area of the pattern is poor form.

Indeed, a 1 oz. load is perfect for a 16 gauge. The shot goes where it's useful to the gunner.

"The price of good shotgunnery is constant practice" - Fred Kimble