Two things to determine:

1) Is the point of impact with your dream load anywhere near the adjustment range of your sights. (Mine was not).

2) Is the recoil tolerable enough to practice with?

Cast bullets have the ability to penetrate even the largest bear skull well below the max level loads the gun will handle, and even if you miss the skull, they will penetrate through a lot of bear before stopping.

I worked up a bear load this year for a cow elk hunt in a "beary" part of WY. I started with a 265gr Hornady RN over lots of W296. My M69 4" shot way high at 10yds, and the recoil was brutal. 10 rounds and I was done. I backed off to 12gr of Herco and a 240gr LSWC from Missouri Bullets, and everything lined up. 25 rounds a session was doable.

Then I bought two cans of pepper spray and a practice can of non-pepper spray. The handgun is a very last resort, before you turn into bear poo. Shooting a grizzly without a permit, is almost as bad as shooting a local sheriff in most states.