The effect of radiocarbon calibration is almost always to increase the uncertainty in the age range - often to beyond a century. To see whether radiocarbon might be able to answer a specific question it is worth checking what the calibrated range is for the period in question.
Typical calibrated ranges are shown here for material over the last 4000 years, based on a radiocarbon precision of +-35years. As an example, on the first plot if you take an object from AD1300 (on the x axis) and radiocarbon date it the calibrated range is likely to be about AD1290-AD1400. An object from AD1700, on the other hand will date to anywhere between AD1670 and AD1950.
These plots are all based on IntCal98, calibrated with OxCal using the probability method. Note that where several dates are available on different aspects of an archaeological context the precision can often be improved.
