My hand load that duplicates the B&P 7/8 oz shell is 16.5 of Red Dot and 7/8 oz. It's the lightest load Alliant recommends. In a 7 lb 9 oz Parker 2 frame VH. It burns clean, shoots and feels identical to the factory load.
Looking for something even lighter for a 1 frame 7 lb Parker and & 7 lb Birmingham Hammer gun went under Alliant recommended loads. Dropping to 15.7 it still burns clean, little less report but really no difference in felt recoil. Reducing to 3/4 oz shot and 15.7 it gets dirty and not sure ignition is a good as the heavier load this from the sound only. Might be able to come up with a lighter load using Clays.
Point is working on the bottom end of shot weight and powder charges there are diminishing returns and you can go too far. I gave up on lighter and shoot the 7/8 oz 16.5 load in all my 12 G doubles now.
Other thing worth considering is the choke. Patterning 7/8 oz loads, B&P or my hand loads, in a modern O/U with Cyl chokes its patterns too open and inconsistent to suit me. Although lot of our club skeet shooters use 7/8 oz. Seems to me the reason light shot loads work well is the chokes are making up for shot load.
My opinion only.
Boats
