I've killed a bunch at ranges from 60-80 yards with a 17 HMR and various 17grain varmint bullets. Neck shots, all dropped instantly. I know tons of dudes who do the same--the 17 HMR has become the common truck gun for tons of folks on ranches in TX.
Any expanding bullet will work from your 223. Something bonded might be nicer. Aim at the bottom of the ear or the middle of the neck. You cannot aim behind the shoulder bc the lungs basically end at the back end of the shoulder. But unless it's a monster any bonded 223 will likely give through and through both shoulders, at least at close ranges. I use 62 grain fusions in my 223 and they zip right through most pigs.
