Re: Subsonic hunting
Personally, I think the best way to answer the original question, while recognizing Greg's very salient points about ethical hunting and humane kills, is this:
If one uses subsonic rounds for hunting, is there a very high likelihood of quick, certain death with a variety of ammunition that is subsonic, either by its design, or crafted by curious, enterprising hand loaders, looking for some fun, or perhaps a "handicap," such as that seen with stick and string? Are you trying to kill a much larger animal with a weak round, than is ethical?
If you are talking about raccoons at deer feeders or perhaps small feral hogs, I see absolutely nothing wrong or unethical about dispatching these pests with subsonic rifle rounds. Of course, one could use the .22, but this is really pushing it for feral hogs. They are to be exterminated, not so much "managed," like more majestic animals, so shooting them is more an exercise of reducing a horrendous menace.
This is why I use subsonic ammo at times. Often, I am deer hunting over a food plot (please no comments about the ethics of this enterprise....I manage my herd in a low-fence and populations in south Texas are above carrying capacity of the range). In this instance, if I see a feral hog, I do not want to disturb the hunt, and a 180 grain Round nose to the head from my .308 does the job quite nicely, inside about 100 yards. I've had deer watching this from 150 or 200 yards, never really knowing what just happened.
If the hog runs off, I am not terribly disturbed by this. I would be if it were a deer.
So, whether I shoot a .45 ACP round, 180 grain round nose over 8.6 grains of Unique, or even my latest concoction, the 130 grain Ballistic silvertip 6.8 sub, over 7.2 grains of Trail Boss, my task is the same. Smaller animals can be dispatched ....quietly / stealthily, with subs.
One must consider that subsonic ammo is a novelty in many ways....a rush for the hand loader, but I agree with Greg that shooting a deer with this type of load really is on the very edge of ethical hunting. You most definitely are going to lose once occasionally with .45ACP,. .308, .300 whisper etc.
This is my opinion derived from over 30 years of hunting experience. yours may differ.