Todd -- In my 2 3/4-inch 20-gauge 1-ounce load, I normally shoot #6 lead to maintain good pattern density, but you could drop #5 lead if you like. I load the larger #5 lead pellets in a 3-inch hull with 1 1/8-ounce and normally have it in my O/U for the second shot.
Here are a few of my pattern numbers from the 1-ounce Blue Dot load that I've used on a good many pheasants.
Patterns from a 20-gauge Browning Citori with 28" Invector-plus barrels and Briley flush chokes (patterns average of five, 30" post-shot scribed circle, yardage taped muzzle to target, and in-shell pellet count average of five).
20 GA 2 ¾” RELOAD (REM HULL, BLUE DOT) 1 oz #6 lead (233 pellets) @ 1200 fps
30 YARDS – SK / pattern 147 (63%)
30 YARDS – IC / pattern 168 (72%)
40 YARDS – M / pattern 146 (63%)
40 YARDS – IM / pattern 163 (70%)
Are you shooting over flushers or good pointers?
3/4oz. 7 1/2 shot at 1150, LM choke is very effective for pointer dog, pen raised pheasant or chukar and quail. your shots are at 25 yards from your feet!
I back up after 4 shot misses with 12ga, 7 1/2 shot 1200fps, 1 1/8 trap loads, often one shot crumpling down target! If not,,, well my second shot is a bit hotter! 5 shot,,, 1 1/4oz 5 shot around 1300fps. may be out there a bit!
If after all these shots and no bird to retrieve, after he has been rock solid,,, My Shorthair looks at me, with a WTF?