I have always used the thickness of as dime measure, but have only checked when I had a problem that was not caused by the most likely suspects, a weak main spring, mainspring screw not tight or shortened by someone or mainspring replaced
To check for .05 Swing out cylinder, press back on thumb piece so trigger will operate, pull trigger and hold it all the way back, Slide a dime up against the tip of hammer nose. Should be close
Besides your mainspring and mainspring screw, check your cylinder's end shake as that can cause it if excessive. Plus, how thick are your clips as there is some variation? Most are right around .040, but I have seen a few thinner than that at .036. What brand brass? Load some empty or fired brass in your clips and measure from case head to recoil shield at firing pin. Should be .014 MAX and less if better. .014 would be the result of a combination of a gun made with max head space and brass with minimum head thickness.
With 2 similar guns doing it I would first check that mainspring screws are tight, then head space, mostly because of brass/clip, combo. Then, endshake and if not any of that I would pop the brass anvil out of a couple spend primers and place them on the tip of mainspring tension screw and tighten it up to see if increased mainspring tension helped.
In my mind the chances of 2 25-2 both having short firing pins is very slim
