Aiming Points for Wild Boar
The minimum calibre for shooting wild boar is a 243 Winchester with 85 grain, or heavier, expanding projectiles designed for game, not varmints. Heavier calibres are preferred. Wild boar are strong, solidly-built animals with sharp tusks and a willingness to defend themselves vigorously.
Their vital areas are relatively small and surrounded by a lot of muscle, thick hide and heavy bone structure.
If you are limiting your hunting to smaller bodied pigs then the 223 Remington with quality 55 grain game projectiles is a good starting point for choice of calibre.