Tom,
The reason the center-neck shot works so well on pigs that everything vital in the next--spine, large blood vessels--runs right through that area, unlike on many longer-necked animals.
Bill Wilson said he learned it from an old-time pig hunter in northeast Texas, near Bill's ranch. It's a pretty neat area--a lot more water and big trees than South Texas--but also LOTS of pigs, many big ones, because there's more natural food.
