As I haven't seen this mentioned, after you shoot 5 shots or so, find the fired patches. They can tell you a lot about what is happening.
If everything is going like it should, the fired patches will have tattered frayed edges but where the ball was sitting aginst the bore, it should not have any slits/ worn thru areas or burned thru areas. The center of the patch should look gray, dark brown or even slightly black depending on your powder, but not charred or burned.
If the patch has radiating slits going outward towards the edges, where the ball was seated in the bore, it indicates the rifleing is too sharp and needs to be steel wooled or lapped to break the edges.
If the patch is burned thru, it indicates a lack of lube or old patch material (or both).
This can also indicate the patch thickness coupled with the ball your shooting is not sealing properly. Increase the patch thickness or ball size a few thousandths of an inch.
Note: old patches become weak over a period of time. If the patches are old, go to Walmart and buy some blue and white, or red and white pillow ticking. Make sure you get the 100% pure cotton kind only. This is reeeeeeaaaaaalllll good stuff for patching.
If a area looks torn, it may have been ripped when you rammed the patch/ball into the muzzle. Check to see that the muzzle is a nice smooth transition from the face into the bore. No sharp edges permitted here IMO.
If your patches are not burned, torn, or cut and the gun is still shooting poorly, check to see if the sights are loose.
If they are tight, then do as suggested by the others and return the barrel to TC. Something is very wrong with it.