failure to fire question

Question
Old single action .380 semi-automatic occasionally fails to fire. Good hammer strike and all the others went off..... what do you think:  weak hammer spring or worn firing pin or hard primers ??

Thanks very much, (FEG M-37 )

Answer
When you say good hammer strike, if the means you see a dent in the primer of the bullet, then it is the ammo not the gun.  If you have good, recent ammo and light hits on the primers then it is gun.

You would have to test it with good factory ammo, if the dents are too weak on primers, then it could be firing pen worn worn down over time, could be broken firing pin, could be firing pin spring is weak, older guns did not have good springs like they make today, so replacing the springs would be good idea anyway, the hammer probable has it's own spring so that could be weak or could have been cut by back yard armorer to make trigger smoother.

Figure out if it is ammo or gun and then work the issue.