[dhoward]

Sounds more like a gun issue to me as well.
Are there drag marks on the sides of the hammer?
Have you measured end shake? Headspace?
It could be the hammer dragging on the sides of the frame are absorbing energy that should be going to the transfer bar. Damaged/ too short firing pin? a 10# spring should be more than enough to light any primers.

Driven firing pin protrusion should be .040"