RU: I used a 300 weatherby for about 10 years. It had, and needed a 26" barrel to burn that bushel basket full of powder per shell!
I find it difficult to judge bears for trophy quality even with a spotting scope beyond 250-350 yards. So even though I had lots of range and was a good shot to 350-400 yards I would never shoot game that far. There are about 1000 things that can go wrong beyond 300 yards and only one is good. I'm not that lucky usually and would never risk the loss of a magnificnet trophy animal through my greed to shoot further then my guaranteed ability to not only kill them, but to find them.
I have never shot and wounded or lost a big game animal in my life. That is due in total to my father beating the responsibility of a killing shot or no shot into my head all my life.
I find it sad to hear of these long shots people claim to make all the time. I just wonder how many were attempted and how much game wounded and not found because they think they missed clean. I have heard and seen these same guys make these claims and then shoot 5 times at a water filled gallon milk jug from a solid rest at 400 yards and miss every time with all the flat shooting cartridges out there. The usual excuses follow, it is just plain unsportsmanlike and irresponsible behaviour in my opinion.
Whats the diference between the 30/06 and the 300 mag? same bullet, same killing power out to 300 yards, same performance on game to 300 yards, 30/06 is cheap, light, no recoil, handy to pack all day with the 22" barrel. The 300 mags give me about 75 yards more practical hunting range beyond the 300-350 the 30/06 has. Since I will not shoot further then that why pack around the additional barrel length and weight? I sold the 300 Weatherby and bought a 30/06 in 1989 and have never regretted a single day afield with it. The 7 pound 30/06 fully loaded with 5 shells and scope with the 22" barrel is a dream to pack and to shoot.
I have taken all the plains game of Africa with it and all the bears but Polar bear. There are certainly better choices for many of those species but it can do the job..... if you can.
If I were buying the perfect rifle for the game you listed the 338 win mag would be difficult to turn down. In my years of guiding experience I have seen bullet diameters under .308 rarely leave a blood trail. Those from .308 to .338 usually bleed good for a while, maybe even 75 yards or more. Those calibers from .338 and over usually bleed plenty and alomost always exit on broadside shots leaving two holes to follow.
The 338 may quite simply be the best all around big game cartridge in the USA today. When I was working in Alaska I always told my brown bear clients the 338 was "just right" and the 375HH was "just in case" we have a problem. With that known you should see that for elk moose and bears the 338 is tough to beat, and nothing from any 300 mag will equal the brute power the 338 has with it's bigger heavier bullets and it's moderate velocity.
The first time you have to search for a wounded bear in the bush with a lost blood trail your going to re-assess your interest in recreational bear hunting. It just does not seem like as much fun anymore! Make two holes when you bear hunt, one in and one out. It's a lot less stressful to find them!
So there you have it some of Jim's philosophy on hunting for the morning.jj