I killem all the time with a 25grn 17hmr, but I confess, I do shoot them behind the eye every time. ive killed bunsches with 223's and 308's( one really cool FN 308 with gen 3 nightvision and a fully suppressed barrel) buuuuuut I shotem all in the head. ive kiltem with thermal to. but ive learned from experience if they sittin still shootem right behind the eye if they are runnin im still tryin to shoot theyre nose off. if theyre within 40yds I got a super black eagle 2 loaded full of buck shot along with an ar-15 with an eotech. helicopters are fun to, also if I do shootem with a bow I will only shootem quarterin away sose I can quarter that arrow through all the little piggys vital organs also with large diameter broadheads. mwahahahahahahahaha.... ahem scuse me I got carried away. 223 will definitely mow pigs down with headshots if you planning on shootin them in the body id go like 30 cal bullets an bigger like maybe 300 win mag or some of the wsm's anything that will cause massive trauma inside the chest cavity. even then you still gonna get some runners.... I don't like runners. I make pigs.. ded:)