Unlike most cuts, brisket is not done when it hits a certain temperature. Yes, the meat will be cooked through at 180 degrees. It will also be fibrous, and webbed with chewy, sticky collagen. A brisket needs to spend a certain amount of time — just how long depends on the individual cut — at that temperature, as the fat renders into drippiness and the collagen turns to gelatin. Meat that feels tough after 10 hours may be perfect at 12. Be patient.