Greetings Karl,
If I had to trim a bunch of cases I'd do it in the mill. Using a V
block and a toggle clamp would probably work well. If you mount the
toggle clamp at an angle such that it moves toward the primer end when
clamping then the case would be pulled tight against the mill table
and the lengths would repeat closely. I have mounted on my Bridgeport
a switch that is controled by an adjustable screw that mounts in the
quill stop. I use this switch to control a solenoid operated air
valve. I have several air clamps that I've cobbled up from air
cylinders and the like. When the quill is raised the switch turns on
the solenoid which in turn opens the air clamp. If you have enough
cases to trim you could save a lot of time. I'll bet a cycle time,
part to part, of less than 7 seconds, would be esay to attain. I could
post pictures of the switch setup and a clamp or too if anybody is
interested.
Eric