I've been following this thread for a while, debating whether to chime in. This can sometimes be a contentious subject. I know it certainly is in the archery community! Sparkitoff, totally agree with spending range time to learn your gun, your load, and your ability. Another thought I had, is that I didn't get into black powder firearms (muzzleloading, or cartridge) with the idea of reaching 350 yards across my back field and dropping a deer (that is the longest safe look I have where I hunt). If that was my goal, I would have purchased a TC Encore hand cannon in .308 (cartridge rifles aren't legal in my zone but handguns are).
Deer season here starts in mid-Sept. I try to get as much time in with my recurve as I can, but am picky about what deer I will shoot (adult doe, and typically let forkies and baskets walk). As a result, I end up shooting most of my deer during the firearms/muzzleloader seasons. I shoot my bows nearly year-round. I practice out to 40 yards in the warmer months, but in the deer woods, 25 yards is my limit and preferably inside of 20. Needless to say, switching over to a muzzeloader is night and day!
My point being, part of this is perspective and attitude. With my TC and Investarms guns, 0-50 feels like slamdunk after bow season. Beyond that is doable, but I want a rest and want a deer that is preferably standing still. I am still working on getting comfortable with my vintage cape gun. I have an accurate round ball load for the straight rifled barrel, but only had time to test it out to 50 yards this year, so that was my self imposed limit with that gun this fall. I shot a deer with it at 30 yards. I hit a little higher than intended, but she is in the freezer. Considering how coarse the sights are, not sure that I would want to shoot that gun much beyond 50, but I plan to take it on out to 75 and 100 this summer, just to see what it, and I, can do.
The bottom line for me is that using a black powder/muzzleloading firearm is about nostalgia, challenge/fair-chase, and hunting skill, more than anything else. Work up a good load for your particular gun. Learn what it and you can do at various ranges and then stick to that in the field. I guess maybe one last thought. If the shot doesn't "feel" right, don't take it.