They say the 'magic' doesn't occur until the internal temp of the meat is 160-something degrees. That's when the fat and collagens start to break down. Then you need to let the meat rise to a temp of at least 185*F (I've read 190, 200, 205 - it varies, depending on whose recipe you're reading). Anyway, if yours didn't get to those temps it will be tough and I don't think it would be fully cooked and unsafe to serve. The whole process takes at least 15 hours.