A tip on reading a slice of brisket...and it can be a little tricky when you just barely miss the mark. But, when you want to understand what happened, here is what you do.
1. Slice a piece that is the thickness of a standard pencil, 1/4" thick. Drape it over your finger, if it bends into a U, then you at least got it done, if not over done. If it does not bend into a U, or it bends into a wide V, then you didn't get it there. This will always be the first indicator.
2. Take said slice, hold it by the ends, about 1/8" in your fingers, turn it so the slice is vertical and pull, slowly and with very little pressure. If it tears right away, or tears as soon as you turn it vertical, then it is over done. This will always be the case. If it takes more than a few seconds to tear, or slips from your finger, then it is under done. This will always be the case. A properly done peice of brisket will stretch for a couple of seconds, then slowly tear, you can see the connective tissue stretch slightly then it will shear.
3. Bite the slice, if the bite meets immediate resistance, and the meat has to be torn, then it is under done, this will always be the case. If you bite, and your teeth sheer the meat into shards, or the meat crumbles under your teeth, it is over done, again, it will always be the case. A properly done slice, once your teeth start to touch, the meat will part in a clean bite, there will be no need to pull or tear the meat, nor will it simply fall apart.
Those three tells on texture will tell you where you went wrong with the cooking time. The amount of moisture in the meat is not a good way to tell, neither is the internal temperature. Sometimes, a brisket just does not have a lot of moisture, you can never rely on internal temperature, by checking with a probe, then corresponding the end result with the probe feel, you will develop a touch for brisket.
I'm feeling bearish, and I'm packing a Wusthof Grand Brisket slicer from MABA
"I'm Armenian...perhaps...but then again...maybe not..."