Well it's a "Hawken" and not a Mountain rifle.
Twist rate; Honestly, they mixed them up so much through the years it's hard to say without actually measuring each barrel,, early ones where a slow twist 1-60, then they used 1-48. Instructions of how to measure twist rate can be found here and all over the net,,
I'd bet your 20yr old safe queen has a 1-60.
Common issues with these older CVA/Traditions are;
1. Accumulated/dried oils at the base of the barrel/breech and drum area. Even minor fouling of oils in the flash channel of these things can/will lead to mis-fires. A good oil solvent and cleaning is very important. The use of gasoline and/or brake cleaner to break down and clear storage oils goes a long way to success.
2. Trigger base plate alignment; The Spanish made gun's use a single bolt through the tang to the trigger plate to "button up" the mechanisms. Decades of storage and Ham-handed owners leads to the dry wood becoming compressed by over tightening of that screw/bolt,, that compression makes the trigger plate ride too high in it's original mortise making the trigger cams to contact the sear arm of the lock,, what happens is the lock won't cock unless the triggers are set. A common problem that can be easily fixed with a simple spacer under the plate in front, or re-bedding the trigger plate.
3. All the goofy trigger break and lock adjustment screws,, there are 3, not just one!
3a; The set triggers center adjustment for the triggers travel break
3b; The trigger main spring tension adjustment
3c: The locks tumbler/sear travel adjustment
All that stuff can be found here in multiple threads,,
You got a good gun there friend, don't fret, there is a learning curve,, but its a short one and there's plenty of help here.
Good Luck,