and 10" 223 is worthless at 250m. I'll hit you at 250m, FIRST try, with 10" CAR, at 250m, EVERY time. You hit the man's torso at 600 yds, first try with 45-70, one time in 50, and THINK you're hot crap.
The 10" 223 will start a 69 gr, .308 BC hpbt at 2500 fps, and it will still have 400 ft lbs left at 250m. It doesn't MATTER what energy your silly assed 405 gr lfp has left at 600 yds, since you'll just MISS with it, anyway.