Rob, I built myself a .40 cal many years ago. I had Ed Rayl make me a custom barrel (7/8" x 36", 1 in 72 twist, .012 depth groves, round bottom rifling) and this bugger shoots (and I kid you not - 1fg, 2fg, and 3fg Goex) all three equally well and accurate. .018 spit patch w/ .395 ball)... The guys at the Range I was shooting with could not believe I was able to load eleven in a row using 1fg without swabbing between shots. Granted, I was only shooting 40 grains at a time out of it, but it performed accurately.
I've shot upwards of 70 grains of 3fg out of it, and it still marks accurately... So my forty is what I call an all around rifle I can shoot any powder or load from 40 to 70 grains and get pretty much the same results every time I pull the trigger.
Now that's just my forty and what I wanted to build at the time.
I've never known a person with a .40 that didn't like it.