The only time you need to spend time wondering about "shot placement" is the not so often opportunity of a sitting/standing shot.
So, go out and enjoy, and let your instinct and reflexes take over. Its amazing what reflexes can do for you in a split second.
The very 1st grunter I ever shot was taken on the run at approx. 180 meters with my old .303 using mil surp FMJs
It was running flat out for cover, and I didn't have time to think of anything at all in the process. My reflexes did it for me.
Its snout was only a couple meters away from dense cover when that FMJ hit and went into the boiler room.
On after inspection, it took out the heart and lungs, but he still ran for damn near 80 meters before he dropped.
It may well have been just pure luck on my behalf, but that's the way it turned out.
So don't get hung up on over analyzing things, and worrying about "what if"
I do not fear death itself... Only its inopportune timing!
I've come to realize that,,,,, the two most loving, loyal, and trustworthy females in my entire life were both canines.