Like I suspect a number of folks, I have “risen through the ranks” with case trimmers.
I started with an RCBS hand turned mini-lathe type. Did an OK job, but was slow, tedious and a bit finicky about changing setup for different calibers. Cases are held by a collet that grabs the case rim, and this tends to introduce a bit of variability in as-trimmed overall length (maybe ± two or three thousands of an inch).
So I “graduated” to a homemade power drill attachment for the RCBS. Made the job a tad less tedious, but effected no improvement on setup or variability. I’d still groan at the prospect of having to trim a hundred or more rounds of brass.
So one day a year or two ago and on a lark, I bought a Lyman Trim-Xpress. This is a motorized unit that registers cases by an inserted bushing bearing at a datum point on the case shoulder. Downside is that it only works on bottleneck brass, but almost all of the rifle rounds I shoot that need trimming are bottleneck. At first, I suspected that controlling trim via the neck datum would be less consistent than the rim collet, but I’ve done some tests and found that the Lyman gives me far greater consistency: ± one thou our so at most. And lickety split faster than the drill-plus-lathe type trimmer.
Lyman came with an assortment of bushings for common calibers; then only extra one I had to buy was for 7.62 x 39, which cost a whopping $7.
So much so that I no longer groan at the prospect of trimming a couple of hundred rounds of brass.