Don,
Here are a bunch of notes I've compiled from other people's cook posts as well as my own experience. Look them over, and see if you get a feel for what you are looking for.
JimT
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Larry Wolfe:
11 lb. roast, room temp for 1 hour, 200º, 128º internal, 6 hours
Jim Minion:
5 - 6 lb. roast, 250º, 125 to 127 internal, 4 to 5 hours
Kevin Kruger:
12 lb. roast, room temp for 2 hours, 250º, 5 to 6 hours
Ron_L:
4 lb. roast, 275º, 125 internal (carry over to 135), about 2 hours
Me:
2.5 lb. roast cooked in the oven at 250 degrees. Done in 2.5 hours, about 130 degrees. Tented with multiple layers of foil. Still warm enough after ½ hour, and done just right.
Me:
About 50 minutes per inch of thickness.
JiveTurkey:
I roll 300 until 130 so its nice and pink from edge to edge.
thirdeye:
I've cooked them with low temps for a very long time, (even my oven ones are cooked at 250°). Three years ago when I got my first BDS, this prime rib at 225° was one of my first cooks.....
The doneness from end to end as well as across each slice will be very consistant.
It was around 5 pounds and was 2 ribs long.
I rubbed it with a Montreal style rub, which is nice and coarse. It went on the upper grate cold with a pit temp around 225° and a couple of small chunks of pecan for flavor. I started with the fat cap down for 30 minutes then turned ribs down for about 2 hours. No other turning and no mopping was required. At 125° internal temperature I removed and rested for 20 minutes. No end-searing was needed.
From "Cooking for Engineers" web site"
About 45 minutes per pound at 200 degrees. 125 degrees for rare, 130 for medium rare, and 145 for medium. Rest for at least 20 minutes