muchatrucha,
What you said is pretty much standard,however the Sharps Borchart, as I recall, uses something like 35 thousanths, for the same problem you are having.Sometimes new guns,now,find their way out of the factory with less quality control than in the past.It may be that longer firing pins were used with the idea of adjusting them in a finishing/adjusting operation, which wasn't actually performed.
Mike