Many folks choose the 12 ga option, usually a pump, for their bear gun because the guns are inexpensive compared to a rifle anyway, because they are usually reliable and effective with the right ammo - sometimes they're effective with the wrong ammo, dangerous bear encounters are usually, though not always, a short range gig, negating one of the ballistic components of the rifle, and because they provide the option of choosing less lethal ammo. But I don't think a pump 12 bore is the correct gun for everyone, particularly not for a recoil sensitive shooter. If facing a dangerous bear, they shouldn't be thinking, "This is going to hurt me more than its going to hurt you." The down side of the 12 ga is recoil, and excessive bulk and weight of both the gun and it's ammo.
Sometimes you don't have a choice, and the 12 ga is mandated by legislation or by company edict, in which case one does the best one can. If the individual is upset by recoil, a gas gun can help, and provides the additional benefit of never short stroking in a high stress environment. But for the semi-auto shotgun to be a good choice, care must be taken in its selection, price alone cannot be the over riding consideration. While shopping it is wise to consider why the gun is being purchased, and if you're inclined to balk at the price, consider the reason you are making the purchase. It is to save your life, so what is your life worth? A good semi-auto shotgun will be more expensive than a pump gun of similar quality. To remain a viable life saving device, it must be given some basic care in the field, and although a good gun does not need to be babied, neither should it be abused. All shotgun barrels and magazines are thinner than their rifle equivalents, and a shotgun that falls over on a rock will surely suffer a dent which may interfere with cycling or firing, or both. Shotgun ammo is subject to rust and corrosion, faster than a rifle cartridge. I make a habit of swapping mine out every 30 days. A Sidesaddle provides the advantage of having extra ammo on the gun, particularly if you intend to carry more than one type, but this ammo, as well as the ammo in the magazine should be checked each night, wiped down, then replaced in the Sidesaddle and the gun reloaded. Another thing I like about the Sidesaddle is that it replaces the trigger group's cross pins with machine screws and nuts, just make sure you don't pinch the receiver so tight that the gun can't function. If one is going to carry more than one type of ammo on the gun, say slugs and buckshot for example, the magazine should be loaded with slugs, and the individual should regularly practice drills which put a buckshot load in the chamber. The Benellis are good in this respect, due to their ability to work the charging handle without releasing a subsequent round from the magazine. Thus the chambered round can be ejected, the buckshot round is trapped between the fingers of the support hand and the recess along the forend, then as your hand slides back, the round drops through the ejection port, you release the bolt handle, and the gun is back in action, without ever taking it out of your shoulder. That feature alone has be considering an upgrade to an M-4 from my 590. If one stays in a tent, it might be prudent to load the gun with buckshot once back in camp, should other tents and people be nearby.
Gun fit, be it rifle or shotgun, is as important a consideration as the gun itself. If the gun's LOP is too long, felt recoil increases dramatically. If the gun fits perfectly whey you're wearing a T-shirt, it will be too long when you've dawned polar fleece, Goretex, and a parka. Some folks are taken with the idea of a folding stock, which is particularly attractive to anyone who travels by small plane or helicopter. These stocks are always too long, and the seldom have a suitable comb to acquire a good cheek weld; the top folders particularly can give you a nasty bruised or even a cut cheek under recoil. My advice is to steer clear. The LOP must be correct and the comb must be at the correct height for quick sight acquisition, and a repeatable cheek weld. One additional element to consider is the size of the trigger guard. Make sure your can comfortably insert your finger in the trigger guard while wearing gloves, without inadvertently firing the gun.
