Thanks for the .45 Colt info. Many people don't realize that the .454 Casull is nothing but a .45 Colt case made just slightly longer so it won't chamber in weaker action that won't handle the pressure.
So, I think the issue is whether the Trapper as a rifle is strong enough to handle the pressures rather than if the modern cases can - they can and do in Ruger revolvers (though not up to the 50,000 cup that the Casull revolver handles).
I also realize that no pistol round at any pressure is a good brown bear stopper. But then, no round is really adequate for an adrenalized browny. They regularly soak up a bucket full of .375 H&H's when somebody makes a bad initial shot and gets them excited.
My reasoning is based on a handy rifle thats adequate to make a head shot and penetrate well enough to shut the bear "off".
I'm not being paranoid, I was badly mauled by a bear only 4 months ago. My partner shot her twice through the body with a .300 mag and she lived to attack somebody else a week later. This was a sow that probably only weighed 800 pounds or so. The boars here go 1500 pounds. If ever confronted with an angry bear again, I'm going for a head shot. You can link to my bear mauling page below if you're interested. Thanks again!
The Bears and Bear Maulings Page: members.xoom.com/keithrogan