I have a factory 6.8 spc carbine barrel sitting on a shelf. I never had a miss fire with it, shooting it on an old early frame, WITH a hammer spur. My ammo was all my own handloads, as I've never seen a box of factory ammo on a store shelf anywhere to try it. My brass was Rem brass, and I full length sized it in an RCBS die. I've shot the Sierra's and the Barnes 100-110's from mine.
I was getting poor accuracy, and it turns out I have a bad spot in the rifling of mine, right in front of the crown. I believe that to be the issue with mine. I've just never bothered to send it back to TC. I will someday though.
Try shooting it without the hammer spur, maybe your hammer spring isn't as stiff as mine. Mine's still got the original spring in it, and I bought it used in '81, guess I'm lucky there. Also, like was mentioned earlier, try "snapping" the barrel closed firmly, could be a barrel lockup issue.