i have a 1955 that has been worked over for competition shooting including bobbing the hammer.it is real picky on what ammo wil fire. seems if the primer is even slightly set to deep it wont fire. tried tightening the spring a bit.but no help. any thoughts?...could firing pin be worn?

The hammer nose is probably fine. Have you checked for end shake?
The rear gage may have opened up slightly.

Other issues could be dirt, an altered mainspring strain screw, or a damaged or aftermarket mainspring. Perhaps you could have it evaluated by the gunsmith who did the action work?

__________________
Ret. LE, FA Instr, S&W Armorer

thanks for the input....will look into it deeper

Is the strain screw tightened all the way down? Someone may have backed it out.

install new firing pin, mainspring and mainspring tension screw.
Are you using reloads or factory ammo.
check end shake

I had a 625 that was only reliable with federal primers as some previous owner had modified the trigger spring screw for the lightest possible double action trigger. With federal ammo/primers, though, it was 99% reliable. I didn't change it, as it was a range gun and just fed it federal ammo.

My 25-2 (1983) likes Federals also. Winchester I had misfiresI tightened the strain screw. Improved reliability

Primer needs to be fully seated for proper ignition.

No such a thing on a S&W revolver.

I'd be looking at a modified mainspring and or strain screw.

Sorry, that's what I meant.

I,ve been using factory ammo. remington works rather well and winchester aint too bad either but some other brands 1 or 2 per cyl won't fire. I have run some reloads thru with the same results.

When I was an active target shooter many years ago I found many revolvers and some self loaders were very specific as to ammo.
Ask any current target shooter and you will find this is normal behavior.

appreciate all the input.will let you know how i make out