If memory serves I read that Hermann Goering was the last man in GE to take boar with a spear, I know he was a morphine addict, but still he must of had brass co`jones, if not case-hardened! Evidently that was his specialty, he gave up hunting with firearms to take boar with a spear.
Still though, I cannot believe that an 8mm would not crack a boars skull, I did it on a small one with a '58 Rem using a slug and max charge of powder.
Boar have become a pest here in some areas of the SouthEast USA, and some huge ones have been killed. One was called "HOGZILLA", taken down in Georgia in farm country that was near 2000 lbs. And another taken in South Carolina near as big, an older Black farmer had it on his farm and could not get anyone to go after it, so he borrowed a 30-30 and shot it himself, took 10 shots to put it down for good. He shot it from the safety of his pick-up truck. Fotos of both these boars were posted on the internet. I know a fellow from here that knows the Black farmer in South Carolina, the farmer is always trying to get hunters to come and hunt those boars, they do a lot of damage to his crops. I got both of mine in Nature Conservancy land, they were tearing the place up and raiding an adjacent farm that was a cabbage patch and apple orchard. Both of them were very good eating. Much more tasty than store bought pork, but the biggest one was not quite as tender. Most of the ol'boys around here use 30-30 or 12 and 20 ga. shotguns for them. But me and my buddy use BP guns.