I shoot a 1-70 twist Green Mountain Barrel in .58 caliber. I shoot 110 grains of powder and a patched .570 ball. Without question that rifle is good shooting. I can normally shoot a three inch group at 100 yards with it. Then somedays it will do even better and some days we do not like to discuss, but it does average a little better then the 1-48 twist. Still, do not sell that T/C barrel short. They are good shooters. It should do you just fine. Like I said, the T/C barrels I own do like powder and can take a big powder charge. If you ever do go to a green mountian barrel and still are a roundball shooter, then go to at least the .54 caliber. That roundball is deadly on about anything you want to shoot. There is nothing wrong with wanting to stick to round ball loads. I did for many years.