I wasn't sure if the sub gauge or bird hunting forum was the best fit for this info, but since I will be using these for rail shooting; I thought this was the most appropriate forum. I also don't figure many will be using a .410 with steel since payloads and pellets counts are pretty low, but thought some might be interested in what I found. I'll mostly use these in my .410 SxS for rail shooting since it is generally a close range (inside 20 yards) affair.

.410 3” Federal Steel Game & Target load
3/8 oz #7 steel (156 pellets) @ 1400 fps

Pattern results @ 25 yards from a Yildiz .410 SxS with 28" barrels and factory flush choke tubes (patterns average of five, 20” & 30" post-shot scribed circles, yardage taped muzzle to target, in-shell pellet count average of five, and choke constriction from bore gauge).

PELLETS/SHELL (3/8 ounce = 164.1 gr)
Count / weight (grains)
157 / 165.2 gr
156 / 164.5 gr
156 / 164.2 gr
155 / 162.8 gr
154 / 163.3 gr
Mean 155.6 / 164.0 gr

25 YARD PATTERNS
IC choke, right barrel, .005” constriction
20” circle (%) / 20”-30” ring count / 30” pattern total (%)
122 / 30 / 152
107 / 41 / 148
107 / 37 / 144
102 / 46 / 148
100 / 45 / 145
Mean 107.6 (69.2%) / 39.8 / 147.4 (94.7%)

25 YARD PATTERNS
Mod. choke, left barrel, .010” constriction
20” circle (%) / 20”-30” ring count / 30” pattern total (%)
131 / 18 / 149
127 / 20 / 147
117 / 28 / 145
110 / 35 / 145
104 / 35 / 139
Mean 117.8 (75.7%) / 27.2 / 145.0 (93.2%)

Good luck!

Joe,
Thanks for posting these.

I did some very basic testing of the same shell but with #6 shot with the intent of possibly using it for squirrel on government land where nontoxic shot is required. Again my testing was very basic, 9" paper plate at 25 yards on 3/4" plywood, (max. distance for my .410 squirrel hunting). I thought that the pattern was sufficient for a .410 and squirrel but the penetration into the wood was lacking when compared to lead, Do you anticipate that the #7 steel shot at 20 yds. to have the "knockdown" needed for rail? (Never hunted rail so I don't know how difficult they are to bring down.)
Thanks again for all of your posts about loads and patterns.

Wildwood -- Yes, #7 steel is more than enough to put down the sora and Virginia rail I hunt. In fact, I've shot a good many with 20ga #7 steel as well as other small birds like dove and snipe. The main issue with a .410 and steel is the low in-shell pellet count which makes it tough to have good pattern density beyond 20-25 yards.
Good luck!