Sorry to be so late getting back to you, but it has been a little hectic here, what with school starting back up.
Whatever you do, have backup with you. Either another hunter with another gun, of a good, big-bore pistol. Bears are large, tough animals and don't go down easily. Don't try for a distance shot, which means you will be fairly close to the bear when you shoot. Bears are very fast and can cover 50 yards to get to you in an amazingly short time.
Work up a good, accurate load for those bullets, working on the heavy side, rather than on the absolute accuracy side. That is important, not only to get the rifle sighted in and a balanced load, but to give you some practice with your rifle. I would start at 90 grains and work up to 110 grains.
I'm not sure about the pellets, particularly in 777. I've read too many reports that they are hard to ignite and especially so in side locks. Many people are reporting they have to drop about 20 grains of loose powder in first to insure ignition. Use magnum caps if you decide to stay with the pellets.
My experience with the 295 powerbelts is that they will surprise you with recoil, compared to shooting modern .270 or -06, and especially when compared to round ball. I can shoot several 10s of rounds of the PBs at a session, unless I'm shooting from the bench. Then, the recoil really hammers me.
Pop the green bases off the PB bullets and put just a little lube (Wonderlube, Ballistol, whatever) in the cup and place the base back on. This will ensure that the base (wad) drops off quickly and doesn't spoil the bullet's true flight.
Go to Wally and get a small baby's sipper bottle. The ones with the flip tube on top. Take the internal straw off. Fill the bottle 3/4 with your liquid bore wipe/bore cleaner of choice and drop it in your possibles bag. I use 50/50 Ballistol and water. Carry extra dry patches with you to wipe the bore after swabbing. Carry an extra nipple and a nipple wrench with nipple pick. Carry a patch retriever button for your rod, to get back that patch that came off the jag, halfway down the barrel. This button can be of the type with a cork-screw kinda wire on the end or of the two bent wires sticking out the end. Both work well.
DO NOT pour powder directly from your horn/flask/bucket directly into the barrel. Pour into a measure and then into the barrel. After firing each round, pull the hammer back to half-cock, flip the rifle around, place your hand around the muzzle and blow into the barrel. This moistens the fouling in the barrel AND blows out any lingering sparks still in the barrel. It is much more fun to pour powder into a barrel if there are no sparks down there to blow it back out at you.
Get a copy of Lyman's BalckPowder Handbook, if possible. There is a wealth of information in there to get you farther down the line.
There are some other things, I'm sure I'm forgetting as I whip this out. Others should be along shortly to add to it.
Most importantly,,, invite me to come along.
I envy you.