The firing pin thing we can fix. The over pressure you describe needs to be discussed. Was it a reload? Or name of the ammo manufacturer and other details would be good.

How did you measure your protrusion and what did you end up with. I prefer a depth mic but a skilled machinist or someone who is knowledgeable of dial caliper usage can make it work. I hope you were not eyeballing it. The fact that you considered making it longer is concerning.