I agree for forming/converting cases, such as 300BO or 300HAM’R, using a medium router with an end-mill cutter (aka Dillon RT1500) is best way to efficiently remove large volume of brass from a bunch of cases. Afterwards can either add a chamfer or run it through steel pins to knock off any burs. Quick & Dirty for cases that get lost in the grass. Perfect for run of the mill AR15.
I have a couple of bolt rifles (300BO) that get top shelf treatment for their brass. The Henderson works great for this job…. No finger cramps trying to hold a short case. Each rifle has its own dedicated stop bolt set to its chamber. I’ve trimmed about 2k of these short cases on Henderson without issue or regret.