Hey Tman, looks like you just got a taste of why BBQ is so fun, and so challenging - all at the same time! We try to "control" the uncontrollable. No matter how good our technology becomes, and how accurate we can control our smoker, there's still one really big wild card in the deck: The meat!
Every piece of meat is made by an animal, and (just like us) they are all different! USDA grading is a "best guess" by the experts at how good the finished product will be, but certainly not an insight to how long something will take to cook! I believe there are so many factors to cook time: Density of the muscle, fat content, amount of connective tissue, moisture content, and probably some others that I'm overlooking. I guess that's the main reason we look at a cook with a reasonable time estimate (like 1-2 hours per pound), instead of saying "smoke for exactly 4.2 hours," like you would precisely do in baking. BBQ is so different! The meat has it's own agenda, and time table!
Ain't BBQ fun? lol! To me, the unknown is what keeps it interesting! Who wants to have a "cookie cutter" formula for every smoke? I like it when the meat throws me a curve ball, once in awhile! That's where "feel" and intuition/experience come into play!
