1911 45 Trigger,s

I,m trying to discover why when dry firing my 45's one of them jumps ( the dot jerks around the black) at release when my others stay rock solid in follow thru. Could the over travel be too short?
Scott

You could also have the hammer hitting the slide ever so slightly when it falls.  This could be from a hammer and pin having too much clearance. Or an off axis firing pin hole in the frame.

Thanks for the reply, I don't think the hammer is rubbing on the slide. If I cock the hammer with my thumb it's noticeably harder to cock than other 45's. I firmed up my grip a lot and its much better.

Sounds like it just has a heavier main spring that the others.

Could be something loose in the sight.  I assume you checked the rail mounting screw and the tightness of the rings?

If I were in your position, I might try swapping items from one to the other to see if you can move the symptom.

Do a test before dry firing the one with the dancing dot.  Give the optic a strong forward push to see if the slide has not moved fully into battery.

I had the same problem and checked the obvious common issues.
It turned out the the mainspring housing bore had drill gauling grooves from manufacturing.
This caused the upper edge of the mainspring to catch on the groove as the hammer fell.
Polished the grooves out and it fixed the problem.