My Win. '92 sometimes miss fires due to the hammer falling into the saftey notch and therefore not striking the firing pin.
This occurs only when attempting to fire a cartridge, not during dry fire.
Regardless how I may slowly or quickly actuate the trigger during dry firing I can not make the hammer drop into the safety notch.
Why does this happen while attempting to fire and not during dry fire?

If you cannot make the rifle misfire during dry fire, sadly to say, the only thing that comes to my mind is you're starting to flinch. Does this happen more so towards the end of your shooting session when you're starting to tire? That's when you may be losing concentration and unconsciously starting to flinch. A flinch coupled with a weak hammerspring could do this. Suggest you have a shooting pard work with you on this. Have your pard "load" the rifle sometimes with one cartridge, sometimes not out of sight. You shoot the rifle and see if a flinch ever occurs when the rifle turns out to be unloaded. If your problem is flinching, you can work this out by only shooting when you still have good concentration, perhaps by shooting at a slower pace. This is just my guess at the problem and I hope I'm wrong so no offense intended. Hope you find your problem and fix it.