I checked one MK-XIX firing pin and it measures 3.167".  The L5 pin I checked was 3.075".

So are you experiencing light firing pin strikes, or were you just checking firing pin protrusion out of curiousity?  When you are checking, how are you doing it?  Are you just locking the slide back and pushing on the rear of the firing pin and don't see anything poking out the breech face?  If so, this is correct, as the bolt is in the forward, unlocked position.  

With the slide open, or removed from the frame, depress the bolt locking plunger (on the left side of the firing pin), and then rotate the bolt. As it rotates, it will cam to the rear.  This is where the bolt is when locked into the barrel extension.  Now while holding the bolt in this position, try depressing the rear of the firing pin.  You should now be able to see the front of the pin protruding through the breech face.