I've been having an issue with excessive extreme spread in my ammo. My rifle is a Savage M11 Trophy Hunter XP with an aftermarket 6mm Rem McGowen barrel pillar beaded in a Boyds Stock.
After trying hundreds of combinations with this gun I cannot get anything below 1 MOA and velocities almost always vary by 50 -100 fps for three shots.
I'm very meticulous with my loads. Headspace is about 0.001" - 0.002" on my sized cases. Bullet runout is 0 - 0.002".

The gun really craters primers even with mild loads. I tried increasing the radius of the firing pin and it helped but did not eliminate the cratering. I increased the radius some more but then the ammo failed to fire. I decreased the radius but the cratering returned. Firing pin protrusion is 0.053" and is not adjustable (one piece firing pin).

This rifle was originally a 243 Win and I checked my notes and even when it was new with the factory barrel it was giving velocities with a high ES which leads me to believe it is firing pin/spring related.

I spoke with one gunsmith who said this action with the one piece firing pin is no good and suggested I get rid of it.
Is it possible to replace the one piece firing pin assembly with the two piece assembly? Any other thoughts?