IF I could have only ONE ML for worldwide hunting, it would be a "plain vanilla" SxS CapeGun in .58 (rifled 1 in 48") & a 12 bore smoothie.
Loaded properly with shot on one side & with a 500+ grain Minie ball in the rifled barrel, I wouldn't be afraid to tackle anything from quail, squirrels & bunnies to African plains game and BIG cats.
(According to numerous 19th Century "white hunters", the ML scattergun loaded with 00 or 000 buckshot and a HEAVY load of BP was "perfection in lion medicine".)
IF I was going after REALLY BIG GAME (Including the Grizzley or Polar bears), I would have the CapeGun done in 10bore with a HEAVIER caliber rifled barrel.
(Some 10-12 years ago, The National Firearms Museum had a .66cal.x 10bore CapeGun on display that had reportedly killed numerous Asian Gaur and "many Tigers & Panthers in British India".= It was built in the UK for a Mogul prince.)
yours, satx