I've used the 28 ga for Sharpies in the Sandhills and Chickens in SE Nebraska for years. I prefer to handload 3/4 ounce of number 7 shot. I bit more punch than 7.5s and the same pellet count as an ounce of 6s. You'll be good to 30 yards or a bit and if you change chokes to accomodate conditions there is no reason you won't be successful.

HTH, sv