Lots of good suggestions here.
Especially the ones about NOT trying to replace the firing pin.
As noted,, occasionally,, the firing pin bushing area get crud in it. Totally invisible,, due to it's location. The simplest beginning fix would be a good ultrasonic cleaning bath. Pull the grips & do the cleaning. Blow dry & do a kerosene bath next. Blow dry again, then add oil,, especially in places that are hard to access.
Test fire then.
And as noted,, try different ammo, especially some factory stuff, just to verify any problems.
Next,, the hammer face could be just a little too long,, and could be hitting the frame w/o delivering enough force to the transfer bar. NEVER try thinning the transfer bar. It's already a "weaker" piece vs the hammer. A SMALL amount of removal of the top of the hammer nose could be necessary.
Ruger parts,, such as the firing pin itself or the hammer spring are all going to be basically the same. A stronger spring may not be the fix either.