Re: 223 Ackley Improved
That's either in a 20" Service Rifle, or a 26" Match Rifle being used for XC-HP shooting, chambered in the standard 5.56mm/223 Rem cartridge. The normal course of fire goes from 200 to 600 yards, but the 80s have seen extensive use out to 1000 yards as well. Pretty marginal out of a Service Rifle, but they do perform well out of a Match rifle. That extra 6" makes the difference. Running the 80s at 2850 out of a Match Rifle is doable at sane pressures, and the bullet will stay supersonic all the way out. The 77s won't, and while I've never seen the Hornady 75s used for this, I have no doubt that they'd go transonic before reaching the target. Not a good thing.
There's also been a push towards the 90 grain bullets, but these are a bit more problematic in a Service Rifle. Those who've had the best results with them are usually using them in a Match Rifle, and still pushing them pretty hard.
The BR has about a 5 grain water capacity advantage over the 223 AI, which in turn has about a 2 grain advantage over the standard 223 Rem; 36 grains for the BR, 31 grains for the 223 AI, and just a tad under 29 grains for the 223 Rem.
Hope that helps.