Originally Posted by thirdeye
On a whole brisket, both muscles will not probe the same. In fact, the additional fat in the point allows the internal temp of the point to rise faster than the flat (fat is a better conductor of heat). Because of this, the point gets tender before the flat. And because of the fat it's hard to overcook the point. So, let the point do it's thing and concentrate on the flat.
For you other question, not all of the flat will probe the same.... Part of the flat overlaps the point and the rear of the flat usually is thinner so it can actually dry out while the remainder is cooking tender. You sort of have to figure out when to call the ball on tenderness. A long rest will help the tenderness and moistness even out, so many folks rest a good long while.
When you overcook, the protein fibers that you have been trying to unwind for tenderness, will start squeezing out the moistness (gelatin) they have been hanging on to and all that goodness goes into the pan or the foil if you have wrapped. The meat you have left is very fiberous and tougher... I do agree with Bludawg in that a little overcooked is better than a little undercooked.
Thanks for the replies. I suppose it will take some practice to get it where it turns out the way I want it too...
It rested for at least 4 maybe 5 hours wrapped tight in foil in a cooler packed with towels. I also wondered if this had something to do with the outcome. It was a longer rest than I wanted but just the way it worked out on that day.