When I lived in TX, I used an AR in 5.56 on deer and hogs. 55gr Hornady Soft Points worked well on Whitetails (size of pronghorns) out to 200yds, and pigs fell well enough to 55gr and 62gr FMJ loads. We didn't walk all that much, so weight wasn't a concern, and shots weren't far. (oftentimes, we just sat in the deer blind, and shots were less than 100yds)
Now that I'm up here in MT, I don't use one, but I still plan to, possibly for river bottoms--but I also have a very accurate AK, and the added punch of the 7.62x39 round would leave me feeling more confident. I'm also working on a 6.5 Grendel configuration that I could possibly use on pronghorn and deer, but I'd also like to get one of the new .224 Valkyrie ones, too. As far as my .308 AR is concerned, it's just too heavy. When it comes down to it, I feel much better taking one of my bolt rifles. If I got one of the new Christensen carbon fiber .308s, maybe I'd use it pretty regularly.