Ron--
Yes, 600-degree grilling temps would have a higher bump--except that meats are not cooked all that long on those temps, necessarily.
A few things: For something like a tri-tip that might be cooked more slowly for the bulk of the cooking time but started or finished with a high-heat sear, one can usually expect the higher bump numbers (especially if searing takes place at the end and especially if the meat is well seared). For something like a steak--something that is mostly or only cooked direct--one can expect higher numbers as well. (I do not use a therm for steaks, I finger-test only, but for most steaks at most thicknesses cooked mostly direct, I pull when the steak just starts to feel that it's at the level of doneness preceding the done point I am shooting for.) If temping, this would be close to 15 degrees shy, but here is a caveat (and one I should have noted earlier for Andrew--Andrew, you out there?): This--determining the bump expectation--is more difficult with rare finishes. This is because 'rare' actually has a wider definition than the other doneness levels, i.e., my rare might be your raw, her rare might be his medium-rare; and because, especially on thicker cuts and roasts, the meat is not necessarily on or in the heat long enough to be able to push through the low interior starting temps of the meat, especially if the meat went in cold. This is not usually a problem with direct-grilled steaks because the heat is high enough and the meat is thin enough that, pulled shy of desired finish, the momentum, so to speak, of the heat rise will carry. On larger cuts, especially if roasted the entire time (cooked direct) and especially if the meat went in to cook fresh out of the fridge, the bump can be lower for rare finishes. This is not a problem for the middle to the end of the medium-rare level, for medium, medium-well and well because the heat momentum is established by the medium-rare point (and, subsequently, one can usually be more confident of higher bump numbers).
