intermitent fail to fire help

I'll get a random fail to fire, maybe 1 in 100. 

So far I'm just practicing so no big deal (actually its good flinch training) but I want to have this running before matches start. Here's what I have for clues;

A 2nd hammer strike will fire.
Doesn't seem to matter my reloads or factory ammo. 
Springfield range officer 45 with their trick locking msh replaced with proper parts.

Any ideas appreciated.

From the cartridges that do not fire, what does the firing pin indent look like?  Is this factory ammo or handloads, and if handloads, what primers?  

For the pistol, are you still running the Springfield super strong mainspring, and titanium firing pin?

Try a new main spring. Also check the chamber in case there is some carbon build up keeping the rounds from fully seating.

What weight main spring is in there now?

With the barrel out, do both the handloads and factory loads drop right into the barrel and then fall out by themselves?

ls it from a particular round or a particular magazine?

Hello Merick,

All good recommendations.  Also try....

Fully strip and clean the slide.  A buildup of carbon, oil, schmutz will slow (cushion) the firing pin strike.

Jim

If pistol has the lightened Ti firing pin replace with the Ed Brown (I believe is right brand) firing pin for the SA. This is a common occurrence.
Jon

I'm not immune to schmutz, but this happens with reloads and factor ammo, clean or dirty.    

All the ils parts are gone and it has a smith alexander msh with 23 lbs wolff mainspring. 

I had no idea SA had a titanium firing pin, but I read up on it and sure enough its something they did to pass drop test laws without series 80 parts.  Going to a non-ils msh likely unbalanced things.  I'll try a "regular" firing pin when I get to it.