1 1/16 Brit 6's gives essentially the same pellet count as 1 1/4 oz American 6's. It's an excellent pheasant load, over good dogs. In a light 12, I usually back it with a 1 1/8 oz reload of American 6's in the tighter barrel, about the same as Steve's 1 1/16 oz formula.
I think the best patterning 12ga standard factory load I ever used was the old Super Pigeon formula: 3 1/4 DE, 1 1/4 oz, about 1220 fps. Hard to find in 6 shot these days in a good quality shell, unfortunately. I did pattern some Federal Flyers against both the hotter 3 3/4 DE (1330 fps) loads, and also against the really hot new stuff. The 1220 fps loads showed a slight advantage over the 1330 fps, and a greater one over the really fast loads. I seldom shoot anything that heavy, but that's what I would look for if I were buying off the shelf ammo.
