Not familiar with the TC rules but generally speaking you might consider a few things.
Shotgun - when you said two devastating shots per turn, are you talking about a barrel into two different targets, or a single target getting both barrels?
- reloading would seem to be a logical requirement. no movement while reloading? limit the number of shells for reloading?
pistols - do you differentiate between single action and double action? Single action means you need to take an action to cock the revolver and another to pull the trigger. Double action cocks and shoots with a single action. So double action could fire twice (at the same target) in the same time
- do you allow for fanning? More "Hollywood" than not, you still might consider it.
rifles - do you differentiate between trap door carbines and rifles (load a round, shoot it, eject shell, load next round) and lever action rifles like the Henry and Winchester repeaters?
- perhaps more accurate if you are using the single shot at a specific target as opposed to levering off 3-4 shots into the general area in the same time but the multiple shots might be a better capability for suppressing one or more targets in the same area, as well as the possibility of hitting more than one target if grouped together. A single shot from either, when aimed, I would thing would be comparable.
Again, these things I mentioned are not based on the TC rules with which I have no familiarity, just thoughts and observations from shooting I've done.