I'd hate to have to use a handgun on a grizzly,--------but if I had to use one in 44 mag, the old Keith load using a 240gr cast over a maxium load of 2400 would be hard to beat. My old Lyman manual shows 19grs of 2400 for about 1400fps. At these velocities you need a hard cast bullet for sure.
Good luck,
Savage