If it's windy, that just means he'll have to get better at adjusting for it. From everything I've read though, the max effective range of .223 is 600-650m (660-710yd.) Hell, adjustable irons are good to like 600yd.
Again, I'd probably go with .308 as the better choice, but, .223 can do it as well, just with more finesse.
Oh, and .45/70 is only good for like 200yd. Though, on that note, a Marlin 1897XLR is on my list of cool shit to buy.