BP rifles can be very accurate. If your that worried then get a scoped in line.
Like anything else animals get cripped when hunters shoot past their abilities. Thats why I limit my rifle shots to 350 yrds max, and dont much shooting past 300 yrds, tho Im able to shoot much farther. I killed an Elk that was already hit hard from a lasered 475 yrds once. Rolled it right down a mountain.
Ive stopped hunting with a few guys cause i couldnt stand their insistence on being "long shooters" when in reality they werent even very good short shooters. These types almost always use .300 Weatherbys, "why always .300 Weatherbys"? They have their yardage drops taped on their arms and all have range finders. And still they do far more crippling then killing.
Shooting under hunting conditions and shooting at wind protected ranges are two entirely different things. Whether bow, handgun, rifle, front stuffer, each weapon/shooter has their limitations and THAT is the deciding factor. Not the weapon itself. If you cant hit past 50yrds effectively with your BP rifle then dont shoot past 50 yrds. I have a short .58 cal BP rifle I wont shoot much past bow ranges.
Theres to much blood lust in hunting nowdays. To much big money hunting who never paid their dues with range time and practice. I myself couldnt even give a damn about killing anymore Ive taken so many animals. I just like sitting out in nature.