308 and 223 ballistics are almost the same out to 600 yards, with a small edge to the 308 at 1K yards.
80gr SMK w/ 2600 MV: 1K yards, 1150 vel, 402in drop & 111in drift (10mph crosswind)
168gr SMK w/ 2700 MV: 1k yards, 1226vel, 363in drop & 100in drift (10mph crosswind)
80gr SMK @600 yd: 1614vel, 88in drop, 34in drift
168gr SMK @600 yd: 1704vel, 81in drop, 31in drift
For cheap and simple out to 600 yards, 223 is a great choice. </div></div>
Holy slanted match-up! We're talking AR platform, so magazine feed is obviously preferred. Now we're talking 77gr SMK in .223 (80 will be too long). For distance work, the 175gr SMK is far superior to the 168gr in .308.