If your mainspring strain screw was not tightened all the way, just that 1/4 of a turn or more could make all the difference in firing/FTF! Also, you mentioned wadcutters, factory ones are very hard to find now, so I will assume reloads. When there is a FTF and then the ammo will fire on the next or repeated firing pin strikes, it usually indicates that the primer was not fully seated all the way to the bottom of the primer pocket. In my early reloading days, seating the primer to below the rim was the thing to do. I used to have several misfires. When I learned to seat to the bottom of the primer pocket, FTF's disappeared.
Fail to fire on guns with the hammer nose firing pin were rare, except on tuned guns or where the mainspring strain screw was backed out. It seems that with the frame mounted firing pin, many more failures to fire have been reported. It seems the factory firing pin was too short, and an aftermarket firing pin that was longer was the appropriate solution.
In other words, it could be ammo, it could be the gun! I have had a couple FTFs with S&B ammo this week, where the cartridge just would not fire, even after multiple strikes with full power springs! Dud primer!
It happens.