On rabbits I usually use #6 shot, ONLY with 3" shells, the difference in the power of the 2.5" and the 3" is unbelievable, I've used 3" .410's on upland, rabbits/small game, dove, ducks, and geese for over half my life, and it's quite dependable, but I wouldn't use the 2.5" shells for more than....well, I just plain wouldn't use them in a 3" gun...I use them for doves and rabbits in my Marlin leveraction, don't really like the results, but it's FAST on follow ups, so I can usually catch a wounded animal with a follow up fast enough.

7.5# is getting pretty light IMHO, in a .410 that is, it works great in bigger bores, but I've noticed more "winged" birds and bunnies on good shots with 7.5# than 6#, make poor shots with either and you'll get poor results, but I've found that the 7.5# shot DOES leave me with more wounded game.

Also, most of my .410's don't like Federal ammo (I've got 7 .410's), my mossberg made bolt gun takes 2men and a monkey to open after the shot with them, none of my ejector models kick them out, some are lucky to even extract them. I've been afraid to try them in my Marlin, it isn't easy getting a stuck hull out of a levergun in the field.