While I've not personally used T's one in our group uses them quite frequently on canadian geese in December when their plumage is very dense. 60-70 yard knockdowns are very common. Kill shots much less frequent than cripples.

Having said that I see as many cripples in the 30-50 yard zone with hunters using Federal 3", 1 1/4 at 1550 fps.

Nothing is foolproof to a sufficiently talented fool.