[twoblink]

Ok, from rereading the bad babelfish translation, I think I understand what he is saying.

There's 2mm of horizontal displacement needed to overcome the sear engagement.

Handy, I think this is why your test might not be correct. The assumption made is that the firing pin tab and the sear have disengaged (without a trigger pull) and it's "slipped off". If that's the case, the firing pin does not fire from the "at rest" position, it fires from 2mm forward more; because that's the "tip" of the sear iceburg, for a lack of a better description.

So I believe while it might fire if you pulled the tab back to the point where it sits, that would not be the starting point in which the firing pin would be if were were a slip. It would be a release starting from the edge of the sear. This is the "ease of spring tension" I think the good Doctor is referring to. 2mm on that is a lot, so the tension might not be the 70something%, and thus not fire. Because the assumption is that the sear platform has not moved rearward.