1 1/4 oz high velocity loads of #5 in 12 ga or #6 in a 20 ga for early season with a light mod choking. Late season 1 3/8oz of #4 at the highest safe load speed I can find formulas to load and nickel plated shot with buffering to boot with chokes starting with light mod to Imp. mod.

And this is WITH a GSP that knows his job. But birds here have enough pressure that in the late season shots are long and few hold for a dogs point.