I don’t live in bear country but would that be adequate if I did?
Most .45-70 ammo is loaded to low pressure so it's safe to use in vintage rifles. Even at these levels, it should be adequate for bears.
In the case of your Browning, it can be loaded somewhat hotter, making it more effective. Here's an example of some "+P" .45-70 ammo:
https://www.buffalobore.com/index.php?l=product_detail&p=328
Its use should be limited to the following firearms: All Marlin 1895 (1895 Marlins are simply 336 actions, with a 45-70 barrel screwed on to them) iterations made since 1972, all Browning 1885 and 1886 copies, Rossi Rio Grande, New England Arms Handi Rifle, T/C Encore, ALL falling block actions made of modern steel such as the Ruger #1 and #3, Shiloh, Christian and Pedersoli Sharps, all Winchester 1886 iterations made since 1915 and all Siamese Mauser bolt actions.
It fires a 300 grain bullet at 2350 fps...a considerable boost over the standard load which shoots the same bullet at 2050 fps. Of course, it costs $75 for a box of 20...but you get what you pay for.
With Grizzly or Polar bear, you want your lead to have high antimony fraction, so the bullet is hard and penetrates. Most Black bears are not so aggressive. Sun bears (Asia) are even more aggressive but not so big and tough, rather like an oversized wolverine!