Drbranso -- Here is some info on pheasant ammo that I've posted before that may be helpful.
If you’re shooting lead shot, then a No. 6 lead pellet is adequate for pheasants out to ~40 yards, but when shots start getting on the long side of 40 yards, you’ll be better off with the No. 5 lead pellet! Of course, you’ll need to choke your load, regardless of shot size, to maintain adequate pattern density for the typical distance of your shots.
When using steel on pheasants, it is best to go with loads that contain #2 or #3 steel pellets. Steel shot lethality research conducted on pheasants by Tom Roster showed #2 steel to be more effective (at all ranges) than either #6 or #4 steel. Yes, #4 or #6 steel loads will kill'em too, but a little extra pellet energy is a good thing on wild pheasants where shots are often taken at going-away angles and can get on the long side. The research also showed #2 steel resulted in fewer cripples than both #6 and #4 steel; and Roster speculated that the #3 steel pellet would be a good compromise between pellet count and downrange energy.
Here are a few of my pattern numbers from 20- and 12-gauge lead and steel loads, that I’ve shot pheasants with, to give you an idea of the kind of performance you might get from similar loads and chokes.
Patterns from 20- and 12-gauge Browning Citoris 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 (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%)
20 GA 3" RELOAD (BLUE DOT)
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%)
20 GA 3" WINCHESTER DRYLOK SUPER-X STEEL LOAD
1 oz #3 steel (145 pellets) @ 1330 fps
30 YARDS – SK / pattern 114 (78%)
30 YARDS – IC / pattern 123 (85%)
40 YARDS – IM / pattern 106 (73%)
40 YARDS – LF / pattern 110 (76%)
20 GA 3" REMINGTON NITRO-STEEL MAGNUM LOAD
1 oz #2 steel (118 pellets) @ 1330 fps
30 YARDS – SK / pattern 101 (86%)
30 YARDS – IC / pattern 105 (89%)
40 YARDS – IM / pattern 99 (84%)
40 YARDS – LF / pattern 102 (86%)
12 GA 2 ¾” RELOAD (GREEN DOT)
1 1/8 oz #6 lead (267 pellets) @ 1225 fps
30 YARDS – SK / pattern 171 (64%)
30 YARDS – IC / pattern 211 (79%)
40 YARDS – LM / pattern 173 (65%)
40 YARDS – M / pattern 182 (68%)
40 YARDS – IM / pattern 195 (73%)
12 GA 2 ¾” RELOAD (UNIQUE)
1 1/4 oz #5 lead (210 pellets) @ 1225 fps
30 YARDS – SK / pattern 145 (69%)
30 YARDS – IC / pattern 177 (84%)
40 YARDS – LM / pattern 155 (74%)
40 YARDS – M / pattern 155 (74%)
40 YARDS – IM / pattern 174 (83%)
50 YARDS – IM / pattern 125 (60%)
12 GA 2 ¾” REMINGTON SPORTSMAN HI-SPEED STEEL LOAD
1 1/8 oz #2 steel (139 pellets) @ 1375 fps
30 YARDS – SK / pattern 116 (83%)
30 YARDS – IC / pattern 129 (93%)
40 YARDS – IC / pattern 111 (80%)
40 YARDS – LM / pattern 114 (82%)
40 YARDS – M / pattern 114 (82%)
50 YARDS – LF / pattern 100 (72%)
50 YARDS – F / pattern 106 (76%)
As you can see, there wasn't much difference between the IC, LM and M chokes with this steel load at 40 yards, and the LM and M both registered the same 5-shot pattern average!
Hope this helps, good luck!