Just in case this can help you...I've been shootiung TC and GM barrels for 15+ years...never had one lose it's accuracy due to any barrel problem.

Buildup can cause accuracy to gradually deteriorate, and I've restored a couple used barrelsI've bought very simply as follows:

1) Get a bottle of Shooter's Choice Black Powder Cleaning Gel, and plaster it in the bore with big patches soaked with it...2-3 applications of it to ensure the bore walls are plastered.
2) Let it sit 10-15 minutes
3) Run a bore brush up and down a couple dozen strokes
4) Dry patch it all out

5) Repeat this entire process 3-4 times

6)Soak the barrel in a large 5 gallon bucket of steaming hot soapy water for 15 minutes,pump flushing itclean it as you normally do.
7) Rinse it in hot clean water
8) Get it 100% bone dry
9) Plaster it heavily with natural lube 1000 while it's still warm

Recheck / relubethe next day to see if more crud has "bloomed" out of the metal...and use a bore brush as paret of evert cleaning regimen thereafter to prevent buildup...this should take care ofthe accuracy concern.

All myTC and GM barrels areaccurate...Ionly buy GM barrels in the event TC doesn't make what I want...examples:
.58cal Flint round ball barrel for a TC Hawken
.54cal Flint smoothbore barrel for the Hawken
.62cal Flint smoothbore barrel for the Hawken