I'm thinking many people who are new to bg, genuinely think that a .40cal wire dart will kill a pigeon. Cs and other companies should have a leaflet or a small guide with every purchase that tell people the capabilities of each dart and what they should and should not try to shoot. I think this small effort will save the sport a lot of trouble.
.40 cal should be used for targets only IMHO yes you may get lucky and bag your game.
Yeah some people might get lucky and even bag a squirrel, it has been done but at the expense of countless trail and error = lots of run away animals with thin darts sticking in them. Bad press, Peta loves this kinda things.