I used to favor big magnums but got bored. Haven't hunted since 78. Then I decided recently to try black powder muzzle-loaders. Bought a 58cal Kodiak Express double rifle.
120 gr of powder, with a 270 grain lead ball makes it a good brush gun for medium game. 200 gr powder, with 570 gr lead bullet is without a doubt more than enough for a brown, at close range.
They hunt Cape buffalo with these, but use a 600 gr FMJ bullet. Traveling slightly faster than the speed of sound, those big bullets have both penetrating power, and high sectional density.
I don't hunt critters anymore, but it is a fun rifle to shoot. Two barrels give you back-up if a brown comes after you, but reload time is so slow, that it makes you hesitate, until you're really certain that you are in danger.
At the Rabbet Creek range, full loads sounded like cannon, plowed up the berm, smoke filled the shooting area. Bought a stock pad after that experience. Even small ladies would be comfortable with 120/270 light loads.