That sounds unusual for it to be shooting low.
There should be more information than being provided.
What size balls, patches and loads are being loaded?
What's the distance to the target and how low is it shooting?
Where in the rear sight notch are you holding the bead when you've aquired the sight picture? Can you raise the bead enough within the rear notch (or just above it) to raise the impact of the ball at 50 yards?
I wonder if the front sight is original, which model it is (a Hawken maybe?) and if it's a kit gun with a K serial number prefix or not.
If it's a factory gun then TC will generally fix the problem for free. Maybe there's something wrong with your rear sight elevating properly. If there's supposed to be a spring maybe it's missing, or the screw was lost and the replacement isn't long enough, or the wrong front sight was installed.
Do you have the flat, squared front partridge sight or a bead post front sight?
Pictures might even help to determine the model and to see if you have a set of factory sights.
There's always the possibility that you're not putting your face down low enough on the stock due to the rifle not fitting you properly. Maybe you require a longer length of pull and can add a slip on butt pad to test that theory out.
I guess that the bore could be drilled off center, but that may need to be left to TC to check out.
I can only fathom what else could be wrong. If you're shooting at 50 yards and your sights and barrel are original TC, then there shouldn't be such a problem.
Are you closing one eye when you aim and using your dominant eye?
Maybe you're relaxing when you pull the trigger and letting the muzzle drop?
Are you shooting offhand, off the bench or both?
I wouldn't change anything until you are more sure of what's causing the problem.
Does it at least shoot good groups at 50 yards?