That's what a 20" AR 223 has left at 600 yds, using the 77 gr match bullet. A guys is NO threat to you anymore at 600 yds, once you hit him in the chest with such a load. He's HAD it, and it doesn't MATTER if he takes a minute to bleed out and ineffectual. NOBODY runs 600 yds in a minute. Nobody is going to be running right past somebody that they've just shot, (not anyway, without shooting them AGAIN.) FUNNY how the 500 ft lbs of a 308 (at 1000 yds) make it a 1000 yd gun, and the 500 ft lbs of a 223 (at 600 yds) make it 'just a gopher gun". I've NEVER seen a goher do crap after taking a 150 ft lb Stinger .22lr hp in the chest.
In fact, it';s a rare prairie dog (considerably bigger critter than a gopher) do anything but flop on the ground, after being hit in the chest with a .22 short solid. 
The SAME pussies will go on and on about how they are 'effective" with .45 ball, at 100m, where the .45 rd is down to 180 ft lbs.
The SAME pussies will go on and on about how they are 'effective" with .45 ball, at 100m, where the .45 rd is down to 180 ft lbs.