Maximum Effective Range

[Forestwalker]

Having shot high-powered rifle competition in my early years, I am still a pretty good shot out to 800 yards with a Garand/M14.

What is the approximate maximum effective range for a .50 cal. rifle. I got a Penn rifle for christmas and love the length of the sighting plane.

I've read history articles from the Revolutionary and Civil Wars about hitting human sized targets at 300 yards, is that really feasible.

Thanks

Guys