No. When you apply pressure to one pin, you're not applying pressure (well, on a macroscopic level to where it would in any way bind it) to any of the others.

No. When you apply pressure to one pin, you're not applying pressure (well, on a macroscopic level to where it would in any way bind it) to any of the others. The pins aren't in a perfect straight line, nor are the holes perfectly uniform, due to the machine tolerances. We're talking on the order of microns here, but that's enough. Turning the slug will thus cause one pin to bind against the cylinder first, and as soon as it clear, the slug turns ever so slightly, keeping the top pin from being able to fall back down (while the lower one can drop back down).