I'm going to be be blunt like Troy.The 38 caliber in anything but a CF Rifle is going to be inadiquate. .44 mag would be my minimum.
People have been mauled and killed by black bears after having been shot with large caliber guns. Getting a "kill" shot on a charging bear is almost impossible. Their gait makes the head bounce up and down. Pull the trigger on a head shot, and its likely the head will be in a different position by the time the bullet gets there. Factor in fear, nerves, poor shooting position, and you can see the scenerio.
Death comes instantly with a shot to the central nervous system, or brain. Shots to the lungs will result in the animal staying alive until blood flow ceases to the brain. In that length of time the bear can cover 20-60 yds, and cause a lot of damage before they expire.
I've read reports that said Bear Spray is the best thing to have for defense. I've never investigated that report, so cannot offer an opinion.
Black bears have a low incidence of attacking humans. 99% of the time, you will see them, even with cubs, and as long as one goes the other direction you will be OK.
If one wants to charge, the thing to do is yell loudly, open your jacket, spread it out to make you look bigger and stand your ground. If attacked and you can't get away, roll up into the fetal position, and wrap your hands around the back of your neck. Play dead. I know thats tough advice but a lot of people are still alive to day, abeit not as pretty by doing that.
NEVER RUN! It will provoke a charge.
Grizzly's are moving into Colorado. Totally different animal. I'm not familiar with your location, but they are in the Northern part of the state, but moving south.
Very dangerous. They can outrun a horse and kill it with a single swipe of a paw.
In Montana, and other states that have the Griz, the bears have learned that a gun shot may result in a gut pile, and move to feed on it.
There are numerous reports of Elk hunters being attacked. while gutting an elk with their guns nearby. The Griz is so fast, they can't get to their guns.
Google is your friend, so type in black bear attacks or Griz attacks, and you will see what I'm talking about.