Take the lock apart so that the hammer is off the lock. Clamp it securely and heat the vertical flat part red. To raise the hammer's nose, you cannot likely bend the round section of the hammer - just the flat, so it needs to be stretched a little so that the nose reaches farther forward...just a bit. Likewise, it needs a tiny bit of a twist inward to align with the nipple...again, just a little.
Dan is spot on, as usual. Your nipple is not seated. The face of the nipple seat must be flat where the nipple bottoms. This can be done with a milling machine, or carefully with a dremel and stones.
I don't know if it's HC for a Hawken or not, but I always split the nose of my percussion rifles, so that the cap has a place to fracture. It makes removing the spent cap from the hammer cup a lot easier. I'll see if I can find a picture to illustrate that.
That's a great looking lock. I've had a lot of trouble finding a hammer like that.