Not only are they using mass spec to get vastly more accurate results than the old radiodecay method, but they are using statistics to eliminate problems with the wiggle graph that comes out of the correlation with dendrochronology. Scientists have combined short lived samples, such as grasses and seeds, if they have enough, to get dates for the start and end of the Kingdoms of Egypt. They get +/- 13 years for the New Kingdom, vastly more accurate than they can get from a single sample.
I was able to combine their results with the Heliacal rising of Sothis, the Eclipse of Mursili, and the lunar dates to get a great set of dates for the New Kingdom Pharaohs. They are sometimes closer to the middle dates and sometimes the lower. It does eliminate the alternate dates for each of these events. Only one set of dates fits all of these points. This C14 work is great.