To start off I personally would stay away from the short magnums. I know that they are a great item but you never know how long that they will be around. The .300 Winchester has been around for a long time and will stay with us for quite a while into the future.

As for the bears, a brown bear is a brown bear, weather it is a grizzly or a kodiak. It is just that a kodiak gets a lot bigger because of its diet.

The .300 will handle any and all of the animals that you have listed quite well. I would stay away from the 150 grain bullets with the 168 or 180 grain bullets being the minimum that I would shoot out of it. Recoil is going to be noticeable but nothing that you couldn't get used to in a hunting situation. Now sighting in the rifle is another matter. Ranges for this round are 300+ yards in a capable shooter and I wouldn't hesitate to take 400 yard shots with it. If you get one with a muzzle brake get one that you can open and close, or remove completely. Quite a few of the animals that you listed require a guide to obtain a tag and they hate hunters that show up in camp with a rifle with a muzzle brake. They are excessively noisy in the field but are alright at the target range where every one should be wearing hearing protection.

As for your shotgun question I have no idea since the only thing that I hunt with one is animals that fly.

I think either of the .300's are fine. But I haven't fired either of them yet myself but my son just bought a 300 Winchester in a Ruger rifle. Of all the short magnums I think the 300 seems to be the most popular and will be around for a long time. I have a 270wsm that I love.

I would settle on something like the 180gr TSX and use it for everything myself just to have one great load without having to change things. 150's are great for deer but the bigger game not as much.

The Bear hunter has a short barrel at 23 inches if I remember before you factor out the brake so the velocity numbers will be a bit less than factory stated numbers. Possibly up to 150fps less. So if finding ammo not an issue I would opt for the wsm for that reason. 

My son is 20 and only 135 pounds by the way. But with the brake I see no problems at all as far as recoil.

As far as shotguns go I have never hunted big game with one and never will unless the area I'm hunting requires it by law. And usually thereduced recoil slug or buckshot loads are due to reduced velocity and energy.

Hope that helps some.

If your really planning onn hunting all those animals, you wouldm do better with several different rifles. I am not a magnum promoter but one cartridge for eeverything would require a cartridge that is suitable for the biggest and most dangerious. I've never owned one but I believe your talking about something like the 375 H&H Mag. Probably the 338 Win Mag would be good too. The 338 Win Mag has something you can't get in a 300 mag, 250 gr bullets.

If your really planning onn hunting all those animals, you wouldm do better with several different rifles. I am not a magnum promoter but one cartridge for eeverything would require a cartridge that is suitable for the biggest and most dangerious. I've never owned one but I believe your talking about something like the 375 H&H Mag. Probably the 338 Win Mag would be good too. The 338 Win Mag has something you can't get in a 300 mag, 250 gr bullets.

You've been given some good info in the replies above. Like Critter posted, the .300 Win mag has been around a long time and all of the animals that you listed have been killed with it. I wouldn't hesitate hunting any of those animals with my .300 Weatherby, although if I booked a brown bear hunt I would probably use my .375 RUM.

And I would also stay away from 150 gr bullets. Velocity isn't everything, in fact too much velocity with a light bullet may result in reduced penetration. The 168 gr TSX and TTSX bullets have worked very well in my .300 Wby for a variety of game animals from a 30 lb antelope to a 700+ lb bull elk.

I am a strong believer in muzzle brakes. They definately reduce the felt recoil and inspite of some internet negatiave posts on them, they have been used for over 50 years on millions of military and civilian rifles under the name of "flash suppressors."

Both my .300 Weatherby and my .375 RUM have KDF muzzle brakes on them, and I wouldn't even think of removing them. I've taken one or the other of these rifles on 3 African hunts and one Texas exotic hunt, and I have never had a guide or PH say anything bad about them. In fact they have all been happy that they have had to do little or no tracking because of good shots that I have made because I was not bothered by the recoil of my rifles.

As to your question on 20 ga slug shotguns, although I have a cantileiver scoped barrel for my 12 ga Rem 870 shotgun, that gun would be way down on my list of guns to take on a brown bear hunt. Slugs do a lot of damage up close, but they loose their velocity (and energy) fast, and cannot compare to high power rifles.

Autoloading shotguns will kick less than other shotguns of the same weight and gauge because some of the gasses or recoil is used to cycle the action.

I killed my American buffalo (or bison) with a single lead bullet from my .54 cal Hawken rifle, which is about the same as a 20 ga slug. The 50 yd shot behind his shoulder dropped him in his tracks.

You were right, the holes in the end of the barrel are called ports, and they act the same as muzzle brakes in that they allow some of the gasses to escape to the sides of the muzzle before the slug (or shot or bullet) exits the barrel. Depending on the configuration of the holes, they will recuce some of the recoil and some of the muzzle "jump."

One thing to remember with any gun is that the weight of the gun absorbs some of the recoil. A lighter gun of the same caliber or gauge will kick more that a heavier gun with the same ammunition.