I've found that placing a collar on the cutting shaft (pic) of my WFT OAL trimmer helps me set the cutting depth more precisely than trial and error. Previously I used a reference case to help set the cutting depth, but I think the collar may be working better, particularly when I use a .0015 feeler gauge (or alternatively, shims) between the collar and the back of the body of the WFT to enable adjusting OAL (base to mouth) to within about .001", recognizing that the WFT indexes off the case shoulder. I got the collar from the McMaster-Carr website and also got shims there. Also, I noticed that turning the WFT at 1500 rpm in my drill press results in small brass bits/particles dropping much less often onto the inside shoulder of the WFT (which causes unwanted longer OALs) than slower rpms, as suggested when I called the Little Crow Gunworks people who make the WFT. Thought this information
might be helpful to you all.
