Was cleaning a friends M10 today and noticed the firing pin hammer spring was ineffective. It's an easy inexpensive fix but do you see that happen often? The firing pin is just flopping, no tension.
Did it break? Lose its coil strength?
If you take the firing pin (hammer nose) out of the hammer you will see that the ends of the slot where the spring is has sharp corners. Over time these corners will eat through the delicate spring and make it break. If you replace the spring, round off or chamfer the corners on the back of the hammer nose slot and the new spring will last a very long time.
The parts book that I have from the Bangor Punta era (I could not find a printed date) shows a hammer nose spring only on the N frame models. All K frame models, regardless of caliber, show only the hammer nose and rivet.
I hope that this helps;