Even though there has been a fairly opinioniated series of posts here, the general feeling is still very civil. That's a nice change for the internet these days!
I would like to chime in here with a few thoughts. First,........ the majority of folks seem to believe in what they have seen work, or fail first hand. This unfortunately often comes with very few experiences. Many hunters see an animal shot and crumpled one time and for ever more feel that load, range, bullet, cartridge, etc etc, it the answer to all conditions for that species. Yet another may see a similiar load fail miserabley and assume the opposite.
In Austrailia a great many hogs are shot with very small calibers. I have seen a couple guys kill 50 hogs in one day. These guys will tell you and argue the point forever that thier little .22 centerfires are the best possible choice. Yet the biggest hogs they shot were well below 150 pounds.
There are others who hunt much bigger trophy hogs who know from thier experience that the thick gristle plate will stop a small soft point 22 centerfire from even going through to the organs. What I think is going on here is some folks claiming that one cartridge is good for all hogs at all ranges regardless if they are boars, sows, feral, cross, or pure european hogs. That feeling is just plain wrong and in poor judgement. Hogs come in many sizes and with very different physical makeup. A sow of 300 pounds will be much easier to penetrate broadside with any gun or bow then a boar 1/2 her size will be. A castrated feral boar has far less of a gristle plate then a pure european wild boar. A feral boar that is intact also has a much thinner gristle plate then a pure european boar.
Its really important to realize they the fella in one part of the country shooting hogs may not have the same genetic makeup of a fella in another part of the country. I doubt that any other big game animal has as varied anatomy as a hog does. All these things tend to influence our opinions on cartridge choice. I have killed quite a number of hogs from across the USA, Africa, and Canada. The differences I have seen are very large in what most folks refer to as the same thing "wild boar".
To settle a series of posts like this the question really needs to be addressed with a bit more focus on the worst case scenerio. That way anything less leaves us with a firearm capable of anything we need. To this I think we need to assume that a maximum 300 yard shot, easily typical in many areas of the west especially California. Then we also need to be able to penetrate at near point blank for the hounds bayed in the thick bush or swamps of the SE USA. Of course we also need to have a bullet that will expand at 300 yards and not explode on the gristle plate at 20 feet. Now that is a very tall order! Finally we need to be able to penetrate through and through both gristle plates on a broadside shot to offer a minimum level of blood for tracking.
So now what do we have to choose from to meet these needs? Consider that less then .308 diameter leaves very rare and limited blood trails. By the time you cover that 300 yards across a canyon in California you will need plenty of evidence to track that hog. You will also need one heck of a bullet to exit the off side gristle plate at that distance. With this in mind it's a very safe bet that nothing under .308 or 30/06 will fit for all around "minimum boar" candidtates. The rifles over .40 caliber also begin to fade as they are not really 300 yards rifles. The exception being the various 416's which would be a very good choice if you can handle the weight and the recoil of these beasts.
So we need a rifle shooting a 150 grain .308 bullet or bigger and somewhere under .375 diameter. These will provide minimum blood trails and flat shooting needed for 300 yard shots out west. They also use premium bullets to solve the 20 foot shots which may come up. As you can see a post like this that asks a question without a hunting style or geographic region is difficult to answer for certain. I should think a 30/06 with a good mid weight premium bullet will work for you in nearly any situation. I have personally killed large hogs with mine in South Africa, Zimbabwe, Canada, tennessee, oregon, Texas, California, Oklahoma, Maybe more? don't recall them all at this instant. It may not be the best in any single situation but its good in them all.
Here is a photo of a pure eurasian wild hogs gristle plate. Imagine a soft point bullet from a small caliber rifle trying to exit this from 200 plus yards. Imagine what a small diameter hole is made in the entry side and how the blood will leak out? Not too good eh! Imagine what the explosive effect of that same soft point is going to be at point blank. Hogs are the only American pachyderm. ( pachyderm is latin for thick skinned) This is certainly an animal that justifies premium bullets when after the more pure forms of Eurasian wild boar in the larger sizes. Ferals and females do not generally have a thick gristle plate anything as thick so they can be taken with far less gun.
Anyhow, ... I'm glad for the civility in the thread and thought I would offer a bit of my thoughts which may not have been well understood by folks in different geographic areas or with the same genetic makeup of hogs.
