I'm no 45 colt nor bear expert. I have some data that shows 850 fps with 8gr Unique and 250gr lead bullet. Barrel length and muzzle energy unknown.
Now, my Hornady #4 manual shows a load of AA #9 powder and a 250gr HP/XTP at 950 fps and 500 ft.-lbs. of muzzle energy. This from a 7.5 " barrel.
I would definitely go with a slower powder and heavy bullet in a bear fight
I'm assuming you have a new model Vaquero. I have an old model with 7.5 barrel that will handle the hot loads but I've yet to try any. I loaded some 225gr JHP"s a little warm that I'll be trying out soon. But I will be fighting paper, not bears.
Peace and good luck
RJ