most of my active Russian Wild Boar hunting in Central California where they escaped from the Hearst Ranch in the late 1930s was with a old Super Black Hawk .44 mag from 1973-2005 period. The first ten years it was mostly over dogs and many times going with the experienced hunters who usually stuck the pig the pits "stretched out " and no guns were allowed out unless ordered to if something was wrong. The old 240 grain Lead semi wad cutter did it's job admirably on the biggest pigs, up to larger than I want to state for fear of being called a fibber !
I have shot them with .44 mag from 7.5 and 4" barrels, also 4" and 8 " .357 with 173 grain Keith and 200 grain custom ammo . I shot a couple with .45acp in a 1911 . Many were shot with my .35 Remingtons in Contender or rifles. Some with .308 and a few with my .375 H&H . We made a couple big cage traps for rancher friend who had pig in strawberry and lettuce field problems where I tested bullet performance and found what worked best. The 320 grain .44 mag loads we cast and made seemed about the best we could get in a revolver, but that was before I got my .454 which I am sure would be slightly better in thru the gristle plate shots. I would say the more European Wild boar in the lineage of pigs the tougher they are. The ones released in Calif. from a couple Grand ranches before world war two were imported for their fierce hunting reputations by those magnificent ranches and the same occurred during the early 1900s on the East coast game estates I believe.
I'd use the .454 as it is more than enough and you want to place bullets fast in the right area .