The problem with a "self defense" shooting scenario beyond 200 yards will generally be considered
very questionable! Ask any attorney and at those ranges, he'll remind you of your 'duty to retreat'. The odds of your being in a protracted firefight in which the courts will find you justified to keep shooting is between onionskin thin and none.
If a malefactor is "attempting to escape" an attorney will advise, "let him/her go". Unless someone is still committing a grievous, class A felony (a specific, ongoing continuous threat to your life, or the life of another) you won't likely have any legal grounds to use deadly force. Yes, range is an issue.
I won't be shooting at people beyond 100 yards. 25 yards or less is even
more likely, and 3 yards is more than a distinct possibility. I can shoot a .30 Carbine even better at these ranges, and 970+ foot pound of energy on an area of .308" on a human target will have a
profound effect on an evildoer. (Let's just say that he/she will likely never play the violin again).
I am not bashing the 5.56 x 45 but I can't see the use of any "extra power" provided by the cartridge for my applications. I simply haven't any need for the longer range or extra power provided by the cartridge. I don't have any "manhood" issues, I just believe in using the right tool for the job. More power isn't always appropriate.
Have fun and use the rifle that best suits your needs; neither the .30 Carbine nor the 5.56 x 45 is best for everyone.