Mathman's instructions for Lee Collet dies::
The first thing I recommend is to ignore the instructions supplied with the die.
The second thing I recommend is to ignore whether or not the press you're using cams over at the top of its stroke.
The die squeezes the neck onto a mandrel, so for a given neck thickness there is a finite limit to how much sizing you can achieve. This die will need adjustment to suit different thicknesses of brass.
Raise the press ram to the top of its stroke. Thread the die into the press until the bottom of the sizing collet (not the die body) just touches the shell holder. Measure the neck OD of a piece of brass.
Run the brass through the die using a full press stroke. It should take no effort since if you're set up as described the die has done no sizing. Turn the die into the press about 1/4 turn. Run the brass in again. You probably won't feel much sizing going on, but give the neck a measurement just to see. If it's still nothing, screw the die in another 1/4th and try again. You'll may start feeling a bit going on as you work the press handle, and if so you'll be able to measure a little sizing taking place.
Rinse and repeat using 1/16th turn in increments for the die. You'll feel increases in the force required for the sizing stroke. Since you're measuring the neck after each pass you'll eventually find two increments where the neck didn't get any smaller. NOW STOP TURNING THE DIE INTO THE PRESS. Remember you're squeezing the brass against a solid steel mandrel which isn't going to give, so even if the press stroke didn't feel like it took very much force the neck is as small as it's going to get.
There's a learning curve to the die, but it isn't hard.
I like to run cases through the die twice, spinning the case about 1/3 turn (rather than the 1/2 turn in the instructions) between passes. This means the parts of the neck that were under the splits in the collet fingers on the first pass will get hit on the second.
Addition from roundoak:
If you have not done so already, take the top cap off and check to see if the collet splits are free from debris and inspect the collet further for burrs and polish if necessary. Then apply a film of grease on the tapered surface of the collet. I use the grease that is applied to a chainsaw bar sprocket tip.
When properly set up it takes very little ram pressure to size the case, if you feel a lot of resistance....STOP and figure out the problem.
