MKL, I'm getting 0.2 gr. variations on consecutive throws and I'm using the small cylinder with True Blue powder.
Well, I don't know what to tell you other than maybe to "tap" thee times on the up and down stroke to better settle the powder. Some reloaders have gone so far as to attach a vibrator to the Uniflow hopper. You can check some of the old threads in here.
My Uniflow is around 20 years old and I have no problem keeping within +/- a tenth of a grain with Bullseye, Red Dot, Unique, H110, WSF, and similar powders.
I have never tried True Blue, so I cannot comment on that one. Your problem sure sounds like powder not settling uniformly in the Uniflow small chamber.
Granted I cannot get that accuracy with the larger stick powders such as 4831 or others I load for rifles, but I've never had a problem with the finer grain pistol powders.
Maybe NickCS will chime in with another suggestion. He loads a ton of pistol powders in a RCBS Uniflow.
Best wishes & best of luck (I know it's frustrating, but one can say that about most of our "fine tuning"reloading issues
).