Here are a few of my pattern numbers to give you an idea of the kind of performance I get from various choke constrictions with a couple of 20ga pheasant reloads that I use. Of course, you'll need to shoot a few patterns with your gun/load/choke combo to confirm their performance.
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 3/4" RELOAD (REM STS, R209, BLUE DOT, WAA20F1)
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%)
20 GA 3" RELOAD (REM NITRO, R209, BLUE DOT, WAA20)
1 1/8 oz #5 lead (190 pellets) 1200 fps
30 YARDS – SK / pattern 140 (74%)
30 YARDS – IC / pattern 150 (80%)
40 YARDS – M / pattern 138 (73%)
40 YARDS – IM / pattern 147 (77%)
Pretty hard to beat a SK/M combo in early season and over good dogs, and moving to IC/IM in late season or in open ag field hunts.
Good luck!