...my suggestion: During setup of the die, with an empty, resized case run all the way up, screw the FCD die down until the collet makes contact with the case mouth walls. You can observe this thru the top of the die opening. Lock the die down. Once you seat a bullet, the case mouth walls will expand a bit, and the collet setting will apply just enough crimp to prevent bullet setback. Because of the design of the collet, you can see how much "crimp" is being done by observing the slots in the collet closing together. Understand that case neck thickness AND trim length will have an effect on this, especially if using multiple brands of brass or range pickups of unknown quality or firing counts.
...using the method of "give it a 1/16 to 1/8 turn" after contact could end up giving your seated bullet a pinched section like an old cocoa cola bottle, and possibility of increased pressure spike at firing.
...some folks use a mandrel of a specific size to control the measurement of the case mouth ID to give a specific amount of "tension", others "polish" the button on their decapping rod to a specific size to accomplish the same thing so that the case necks OD (thickness) becomes less of a factor.
YMMV
