My T/C barrels both shoot pretty well. Both are 20" stainless-fluted with the Williams Guide rear/Firesight front combo.
The .45-70 is capable of shooting 3-shots into one hole at 50 yards, and around 1.5-2" at 100, using the irons. Right now the forend is warped, and I've been working on relieving the ears to get it to shoot straight again. I may give up and get a new forend at some point, but we'll see yet. FWIW, it's the "FlexTech" forend which is giving me trouble. It seems pretty lightly molded and I suspect too much heat from shooting too fast did it in.
The other is a .50-cal MZ. It will shoot about 1" at 50 yards from three shots, and 2-3" at 100, with a 250gr Shockwave with the Superglide sabot and 2-T7 pellets.
I suspect with a scope or finer irons, those groups could be improved. The Firesight is a good field sight, but subtends alot of target and makes for a very coarse sight picture IMO.