9 shot is useful in the .410, particularly in the 2 1/2 “ and 2”” cartridges where the small (or in the 2” tiny) payload means that pattern density is likely to fail before pellet energy.

For some reason in British loaded cartridges the 2”” seems only to be found with 6 shot, although I have ( but won’t use as they are undoubtedly corrosive) a part box of Eley pre WW2 2” loaded with 8 that were probably intended for snipe.

I agree that in the 3” .410 7, 7.5 or 8 are more sensible choices.

Parabola