doghntr,
It's probably your operating style, and you just need some refinement in how you throw the charges. The Uniflow is a good measure, and is pefectly capable of throwing prety consistent charges, but there are some fixes that you could incorporate. A powder baffle is one that may help. As expiper said, the mic will help you return to a given setting, but won't help with the variations. One of the big issues here is probably what Boyd touched on; powder type. If you're throwing IMR3031 and expecting it to be within +/- a tenth, forget it, it ain't gonna happen. Don't care whether you're using an unmodified Uniflow or the most expensive custom BR measure out there, that powder just isn't going to throw that uniformly.
Be as consistent as you can in every throw, from how hard you turn the drum, to how hard it stops at each end of the throw, how you grasp the handle, any side pressure you put on it during the throw, everything. If you feel something different in the throw, or feel it breaking kernals, hanging up, whatever, toss that charge back in the hopper and throw again. Guarantee you, that charge, and likely the one behind it will be significantly off the intended mark.