In my circle of friends, I have one group that all shot a .40 for deer; one was the builder and made the guns for all the others. I don't think they ever lost a deer; they didn't take any shots over 100 yards and most were much closer. I think they shot 60gr of 3F behind their patched balls for deer but I am not sure.
One friend that had a great record for putting deer down shot a gun with a GM barrel, 1-48 twist and found that a REAL bullet was a tac driver in his gun, in a .40 his bullet weighed 175 gr and was about the same weight as a .50 ball.
I have the same GM barrel in my .40 but I haven't been able to duplicate my friend's accuracy results with the variety of conicals that I have tried, my rifle will cloverleaf balls at 50 yards though.
Having shot a lot of deer with a .44 and had rather scant blood trails, (I recovered every deer I shot with that gun) I have been hesitant to use my .40 on deer even though I know it will get the job done, it is all about bullet placement.