Ok, before you cut Dr. . . .
Reducing bolt head height wont change timing. All it will do is move the bolt arms closer to the hammer cam so they can be picked up sooner (of course, checking for burrs on the edge of the notches should be done first).
Cylinder carry-up won't change nor will bolt drop or lockup.
On the other hand, shortening the hand will retard cylinder carry-up which will cause earlier bolt drop (in relation to cyl position) and latter lockup (Possibly after sear/full cock notch engagement. The 3rd click).
One caveat, there could definitely be a burr on top of the hand which is raised by repeated spinning (Hollywood style!!) of the cylinder. Of course, the same thing will happen to everything else as if shortening the hand but, it should/would be a return to the original timing.
Just something to think about.
Mike