Winelover
North Central Arkansas
The part your looking for is the optional micrometer adjusting stem............it's all black with white graduations. The one your describing is the standard graduated stem of the Uniflow.Just went on their website. No accessory micrometer drum for the Uniflow. I got mine from my wife's cousin when he passed. Have no idea how long ago he bought it. I would think at least 20 years ago and probably more like 30. Different arrangement than the current model. On mine the threaded piston screws into a bushing that screws into the drum. You adjust by turning the threaded stem on the piston. Stem has a knurled lockring to hold the setting. My guess is the micrometer barrel is an assembly that screws into the same 7/16" thread in the drum that the bushing screws into. The new drum is also drilled and tapped on the side for a locking screw. I'd have to go back and look. But I think the stem on mine has a flat that is graduated. So, knowing the pitch I can make a few measurements for one full turn. Knowing that, I can calibrate the drum markings to give me tenths of a grain. The RCBS stem is a much finer thread than the Redding. It looks like the micrometer barrel is fixed in place and when you turn it, it moves the piston stem in and out of the drum. I prefer mine design and I'll make the micrometer barrel to move with the stem and read on a fixed barrel that will be part of what screws into the drum.
Not sure why I'm getting all wrapped around this. The Uniflow served me well. The Redding added a bit more precision which is kinda nice to have. No reason the Uniflow cannot provide the same or even better precision.
Oh, and the current uniflow only needs on drum.
In contrast, here's a picture of the micrometer adjustment on a Hollywood measure.