What one can, and what one should may be 2 different things. Before I would engage a game animal at a certain range I would have practiced that shot at equal or longer ranges in field conditions and convinced myself that I had sufficient skill not only to apply the techniques, but also to know when I might not be able to deal with the specific weather conditions.
I will admit that I have been "winging it" with wind conditions, but I have my Kestrel with AB software paid for and just waiting for them to start shipping... Another 2 weeks and I can begin scientifically testing wind correction in the field.
Frankly, 400 yards on a relatively big target like a deer does not sound like a heck of a challenge. Now a coyote with 6" of body depth at 450 yards (which never stops moving) is another story. Except for wind, I think a 600 yard shot on a deer is equal or easier than the 450 yards shot on the coyote. But using reduced BC bullets makes everything harder, especially if there is a bit of wind blowing. I went through this learning curve really fast when I started coyote hunting
and i was told to get a 223 and load up 55gr Vmax bullets. 1 year later I concluded that everything I had been told had been by people who made those recommendations was wrong and was based on shooting coyotes in brush at distances of 20-50 yards.
I just got through watching a DVD "The Modern Predator Hunter" by Byron South, and what a shambles it was. I should have known as soon as it started with the old fart showing off his brand new LaRue AR-15 with EOTech red dot and 3x flip up magnifier how this was going to go. Basically for more than half the DVD the guy misses almost every shot and the shot gunner scores almost every hit they make, all the way past 40 yards... I think the longest shot was ~120 yards. Later in the video he replaces the red dot and magnifier with a "real" scope with a red dot mounted on top and actually scores a few hits, but again all less than 150 yards. Lotsa bullets = lotsa misses more often than not.
Unfortunately I don't live where he does, around here I have yet to see a coyote come in to a call. But every time any stray through where I am set up, at least 1 bites the dust and the last time it was 2.
Instead of looking at the bullet velocity and energy (which logically favor a high BC), how about adding a 10mph crosswind and looking at bullet drift ? That is harder to compensate for accurately and ultimately is the most significant factor in deciding whether a shot is a go or no-go.