My late friend, Don Latter, shot his first Wild Boar in the chest with a .62 Caliber rifle. The ball traveled the length of the boar, stopping under the skin on the opposite rear Ham muscle. The boar was about 250 lbs., It stood still, shaking, until it collapsed and died. Don had reloaded his gun, primed his pan, and was aiming at the boar when it collapsed.
3 of us went for wild boar the next year. I shot mine in the spine and my .50 cal. RB failed to break the Vertebrae. Terry shot his with a .54 RB, with a broadside shot, which penetrated, but did not stop the hog. George shot his using his Brown Bess and a .75 Cal. RB. His was also a broadside hit, but he needed a second shot to bring the boar down.
AFter examining wounds, and discussing shots, range( all were at short range, well under 25 yds) we decided to recommmend Conicals be used for hunting boars to our friends.
I am convinced, from experience( including a subsequent Boar Hunt about 12 years later), that the heavier RBs will do the job, but I am speaking about .58 and larger caliber RBs. George's experience just shows that some animals are just not going to go down easy no matter how large a RB is used. We were all surprised that George's boar did not go down with that first shot.